overall nice setup but I would change the mobo for something else, maybe a little more expensive but worth it.
Instead of buying a new case grab one used, some places even throw them away in bunches, full of useful stuff like fans, hard disks, additional ports, etc.
Omiting the OS is a mistake in this build, obviously for gaming you don't need to have the latest crap system from windows as a heavily modified xp version will blow the doors of vista or anything else (and be more secure and stable) but you know some people like to have whatever is the new kid in town. And they complain on the "you don't count the vista OS here" fact while forgetting this will be a gaming pc...vista sucks for a gaming pc.
With a nice pc like this I would go with dual-booting: a lightened xp version for playing games and a good linux distro for everything else that takes advantage of all the qualities of this pc.
Overall good article for everyone.