Long story short, want to build a machine for means of storing MANY photographs in various files ranging to Hi-Res JPEGs to TIFFs.
1st, I want to say that keeping that amount of pictures on an external HD is a no no. Ever have one go bad? Trust me, you don't want to.
The set-up I am using pretty much does the same as what you want. I use my slaves for more than pictures, I back those up on 750 zips.
This is my set up-
Cooler Master Wave Master
Athlon Barton 3200
1536 mb PC3200 ram
BFG GeForce FX 5900XT OC 128MB
80, 120 & 160 hard drives
Check out the link for the mobo, I chose this because I can hook up a lot of IDE hard drives. I can also hook up multiple optical drives. The board has a lot of potential to grow as you need it. It also has a feature called Gigabyte backup. I load windows, load mobo drivers, then Windows update, install browsers & Office & Works.I make sure everything is registered by opening it once. I scan with Panda, then reboot & run the backup, once that is done, I install my AV. If for some reason I reinstall windows, it is an F9 click away & I'm back up and running in a few hours.
The case I may not recommend if you put HD's in and take them out. It is pretty tight in there and unless you pull the mobo tray out, you can't easily swap drives. If you don't swap drives, it's a great case. I like that the power button is on the outside, and that my drives are hidden by the door. Pet peeve is having to look at different color drives than my case. I love the fact that it has the sound port on top as well as USB ports on top also.
Video card- BFG is a good name, you could get away with their cheaper line. When I bought mine it was more than what I needed. BFG has a lifetime warrenty. I dislike ATI cards because they are a PITA to upgrade drivers. If you do not use a driver cleaner your asking for trouble 9 times out of 10. From what I've seen here with the ATI card we have, one day hubby will be doing something & his screen will freeze, it's usually a sign that his drivers need updating; I'm not big on updating- why fix what isn't broken?