Vista seems to be the only issue I see. Go XP Pro, lot easier on the memory usage. With 2 gigs, you are just barely in the clear after the OS finishes it's take.

If you were thinking of SLI (I know I only see 1...), don't worry bout it. SLI + WoW = bad from my experience and other benchmarks I have read.

Personally, I can run 7 box on my rig and it's nothing special, while running IM, Vent and assorted other crap (mind you, that's 7 boxing and laggy coming into Org...6 box no lag thanks to Symlinking!)

AMD 64 X2 5600+
4gig mem
Some junky vid card...GeForce 8500GT
1TB 10k rpm Drive