The whole point of getting an SLI motherboard is to get TWO GeForce 6XXX, SLI compatible. Getting a single GeForce 6600 GT is decent for a gaming rig (still TWO GeForce 6600 GTs are slower than a single GeForce 6800 GT), but not good enough for today's standard "gaming" rigs.
Dump the ASUS SLI for the GIGABYTE "GA-K8N Ultra-9" NVIDIA nForce4 Ultra Chipset Motherboard
, save $65 there and invest in better video card, like an ATI Radeon X800XL Video Card, PCI Express, 256MB DDR
($299 at your local COMPUSA), the X800XL is pretty much identical in hardware and performance to the GeForce 6800 GT.
SLI is nice but for your budget, I wouldn't even dream of SLI, besides is very pointless to me. Spending close to $700 just for bragging not a very smart idea. The hard drive is a very good choice, manufacturer gives you a 5 year warranty on it.
I only use Thermaltake PSU because of their nice little feature "Automatic Temperature Control", so that's a good choice.
Corsair Value ram is fine, I guess, but I would recommend memory with better timings, like the PDP SYSTEMS Memory Dual Channel Kit
with Cas Latency 2-3-2-5-T1 (memory out of stock but they get it very quick, but it sells very quick also).
I'd change to that....................