Hi Anti_Hero, welcome to GeeksToGo!
Your parts look very nice, there's just a couple of things I would change.
For the OS, since you're getting 8GB, I suggest you go with a 64-bit OS like the Vista Home Premium for $79.99
. In 32-bit OS, you'll only be able to use ~3.2-3.5GB of your RAM so you should go with a 64-bit OS because you'll be able to use all of your RAM. Vista Ultimate is too expensive and the extra features it has, you'll probably won't even use. Read what features each edition has in this comparison chart
For the video card, I suggest you go with this HIS Radeon HD 4870
because the manufacturer has great customer support and warranty compared to Sapphire.
I also suggest you look for a bigger case since you're going for Crossfire and these cards generate a lot of heat. And if they do overheat, you'll be experiencing a lot of problems with your computer.
Note that you can opt for the 4870x2
as it consumes less power (and you save money by going with a lower watt power supply). Another thing, what resolution would you be playing at? You might be able to save money by going with just a single 4870 because its powerful enough to play in 1920x1200 resolution.