I'm taking the idea of some of my PM's out here to this thread so eveyone can see. It seems that there's many of you with this same question, then more on top of that.
Let me tackle the basics. For starters, you sure can get away with budget cooling. If that's what it takes to get more involved, then I'm all for it. Big top end coolers will always be nice to have, but more than a luxury than need. Need calls for the demand, and the demand to OC the beans out of systems made the move for some of the companies to make some very nice equipment. If you don't want a system that will pretty much take the "it's my cooling system's fault" out of the equation, then you don't need fancy pants parts. Besides...a system is always more than the parts themselves...more on that possibly. I started with a kit, and I'm sure many others did. If they didn't, then they don't know really why they're using top end parts...right??
One more briefing on overclocking. A $50 heatsink/fan can get a 2.4C to 3.4Ghz, and a 550 (3.4) right on up to the 4Ghz line. It'll still be relatively hot, but it'll be possible. Water hasn't really upped the limit for me, and I may get 200Mhz due to the better heat transfer. I place most of my good OC's on choice parts from good vendors. If I get something that I don't feel is up to par, it goes back. And I have the very rare means of handpicking my CPU's. I know prior to throwing down the cash weather it'll go or not. So...a 550 on water may just top out at 3.8, no matter what you throw at it. That's tough luck I guess.
Ok, the Reservoir:
It's not needed. What it does do is a couple small chores. Water systems get air in the lines. It just happens. "Air" is part of the H2O, and on first runs, you'll find bubbles comming from no where resting in some places. A res gives the system a place to get the entrapped air out of the lines and circulation. Air passing over the Waterblock isn't as good as water passing over the block, so we want it all out of there.
It also takes some of the maintenance out of having a water rig. Fill it up with you own mix, and walk away. You still need a way to put water in initially, or top it off later...so they make T-lines. It's nothing more than Placing a "T" in the line, where one of the legs goes to a fill port. In normal operation, it's capped off of has a shutoff valve and isn't part of the loop. If done right, this can kind of be a reservoir too. Example...the pump is mounted low, and you place your T here, with the line running straight up to the top of the case where the fill port is. Now, when using 1/2" tube you have the same idea of a reservoir, just smaller.
Now on to the most asked question: 1/4", 3/8", or 1/2" tubing. It's a question all over the place. 1/4" is what the folks across the pond use. I won't go into 1/4", because it's really not an available option in the states. Everything is built for 3/8 and 1/2" lines. If you want to watercool a SFF PC, the I'd use 1/4" in a heartbeat, but it'd have to be inported stuff or DIY.
3/8 and 1/2 are so close to each other, too much emphasis has been placed on it. I've personally only used 3/8" on every build up until this last one I'm still piecing together. I've never been in a position where I said, "hey, it's not getting enough water flow". Going back to where I stated I buy good stuff, perhaps this can be the reasoning I haven't had a problem because I've used very good pumps. Anyway, if you want a perk about the 3/8" stuff: When used with a big pump, it offers more velocity when compared to using 1/2". Taking Danger Den's idea of accelerator nozzles, you'll catch my drift here. But when water exits a restricted space (no matter how large or small), it changes velocity one way or the other. It's known as the nozzle effect. Pressure goes up, and velocity goes down and vise versa. Anyway, if you increase velocity right over the die (and the pressure at this point drops), then it'll cool that area better given our current design trend of these blocks.
On that, I'd like to add that the part that actually sheds this heat (radiator) slowing it down is good (oposite of what I just stated above). Turbulance is more important here, and this is one of the reasons you get bumpy pins on air HS/F's instead of polished smooth ones. With either choice, the designer has to make a trade off and picks one or the other (polished and fast, bumpy and slow). In radiators, slow w/ high volume has shown to be better. So, to make up for any restriction, they give it more tubes, but more passes (single row, double row...if you've looked for a radiator for a car, you've witnessed this).
Material. Copper should be the water block's material. Aluminum doesn't cut it at this point in the system. I don't even like when they use aluminum with a copper core. It's not expensive stuff, so use it everywhere on the core. Silver has better properties, but as you know is expensive. Danger Den has a line of these that are 3 times as expensive, but don't show that much improvement. I say that this is because of the simple design principle used thus far. If it were more complicated than a fairly quick pass over ribs or short mazes, then it'd show more worth. But, we don't have that design yet and copper is the best so far. In a radiator, there's no excuse not to get a copper one. Copper tubes and copper tanks are out there, even if it's just a heater core.
-Lexan tops are "fine", but I don't trust them. I've cracked one after a year's use that ended in a slow drip. Nothing hurt, but surely nothing that I want to leave on all the time unattended like I think should be the level of trust. I add the $6 and get the brass tops from DD. Swiftech doesn't have this problem IIRC, and all are metal of some fashion.
-I won't go into the chemistry, as I haven't perfected this either. Right out front I'll say that I use water wetter and Asetek Algae control. I have the water wetter on hand all the time anyway, and the Algae control isn't that expensive. Look through the forum for the take on bottled water that's perfect for Watercooling for it's PH content. It's a good read, and I use it even though I disagree with some of the facts (adding water wetter and algae control changes the PH anyway, but it's nice to start at a nice "standard").
You'll NEED some type of corrosion inhibitor. In my system, I have copper, chrome, brass, and I think aluminum all in one loop. Electrons feed on this and one of these (or all) will start getting into trouble. Automotive antifreeze has these properties, but you don't have to follow their mixing procedure for optimal use in a PC. There's many more types of inhibitors, so just find one that you think is best and use it. Oh, and I've tried the FluidXP out, and it's not up to par with me. It didn't cool better than water, and it really wasn't non-conductive technically. I wanted to try it out after that top leaked. But after sticking a couple leads in there from a fluke, I got a fairly low ohm reading. I won't throw this on my computer and expect nothing to happen, and it was expensive...so what's the use? I'm still trying to pry the mix we use at work out of the mechanical engineer's head. It's a company secret for some reason, so it's not supposed to be spread openly. But I do see Hydrogen peroxide jugs here and there, and some really smelly anti-micro-organism cans (empty) in the trash bin. Interesting...
I'm planning something in this next build with something I learned in the Navy, and that's the use of sacraficial anodes. Simply put, it's a small disposible piece of Zinc that gets the burden of corrosion and not the important stuff. Once it's either eaten away or gunked up, put in a new little piece. We'll have to wait on the verdict. (The anodes I find are all huge, so making little ones may not be wise price wise). Another thought is placing a negative charge on all the main components through some buss, but I'm not sure on how to do this correctly on delicate components, and may only increase the chance for corrosion.
Silence. It really is golden! One low speed 120mm fan to cool your entire system is all you need. I use a Panaflo on my radiator and it's no louder than the PS fan. Using a probe (probably incorrectly), I found the Panaflo fan to be 26db at-speed and the 80mm in the PS to be 29db. That's quiet IMO. If for no other reason, then water will shut out the old "I have 12 fans..." debate. I always have asked "why!?". If space is a concern, then how about two BlackIce Micro's in series with 80mm's mounted? Most cases have blowholes now, so there's one spot. Then another somewhere else. Take advantage of this if you can't have an uber-radiator.
Stick with a design in mind that keeps plumbing in series, not parallel. If water is given a choice to go this way or that, it'll make it's decision based on resistance. What if the choice it doesn't take is the CPU core and instead your HDD's? What a waste. If you want multiple blocks and argue that heat will build, you're right...so take that into account. First drop should be the CPU, and that's all that matters. You can make a quick jump to the northbridge if you want as they really don't make a lot of heat to pickup and pass on. The video card can make a lot of heat, so try to keep it toward the end of the pass. Put it this way, running warm water over the GPU is still better than hot air and a loud fan. I'd rather have this than passing warm water over the NB and HDD's. That's my opinion anyway.
And to end with a final thought, alternative cooling is the trend of the future. Air has limits, is antiquated in theory, and makes sound. After looking at all these bizaar designs out recently, you can see the stretch these companies have to take for good cooling. So, if 90nm is hot, what about 65? Now that AMD has 90nm procs with the same thermal issues you can't really say "Intel did it wrong", and as their core speed increases I expect to see the same 100+Watt ratings. So, think ahead here. An entire water rig can be transfered to a totally new build. Just replace the block or adapt it. 2 years from now with your CPU with 4 cores, you can just bring over your old water system and keep it cool and quiet. Until they start replacing the OEM HS/F with water systems, then this is still the way to go.
But do this all with reality firmly in check. Do you want a $300 setup, NEED a $300 setup, or just feel like spending some cash? $150 kits are great intros, and will (no pun intended) get your feet wet. They're all upgradable too, so if you don't like the part, yank it and put in what you do like. But at least with a kit, you know why you don't like something because you've tried it.