You won't need 12 GB of RAM.
I'd step up to the i7-930, as it's basically the same price for a better CPU.
Trade the board for a Gigabyte GA-X58A-UD3R for more future proofing.
Two 5870s is kinda of a waste. It'll cost you $800 when you could get a 5970 (technically the same thing) and only spend $700.
As far as FPS, I don't know. I doubt you'll get playable rates with Crysis, as a single 5870 barely gets that at 1920x1080. Crossfire scales something like 70%, but you're tripling your resolution. The other games should be fine though.
As far as a bottleneck, it will always be the GPU for gaming.
I already have a gpu/motherboard btw, lol.
Question is 5870 in crossfire enought for playable fps rates with eyefinity, dirt2 f.ex.?