That 680i chipset is old tech. Get the new x38 chipsets if you want to be able to upgrade for the next few years.
I agree
2 video cards in SLI only gives you about a 38% increase in speed, but costs double the price. So it is not worth it in most peoples opinions.
Again, I agree
The raptor is nice, but you will need a second drive for all your files. Only put the OS and your games on the raptor, and get another drive for everything else
Agree...
Antec 900.

Not a fan of it! (read my other posts on why I don't like it)
The antec 900 is alright, but this case is cooler imo.
XP is better for gaming, it will give you better frame rates. Yes I know it does not have DX10, so what. DX10 is nothing special if you ask me. At least not right now.
Here's where I disagree. Xp is better for gaming, but not by much. Despite what most people think, Vista is only slightly worse. When I had my 8600gts, I ran 3dmark06 on the same system with in XP/Vista. It was only 300 points higher in XP. I'd get Vista if I were him.