wait a few weeks and you might find an $800 quad core with an hd 4870/5850 video card and windows 7 pre-installed. it would be perfect for you.
I'm looking to buy or build a new desktop for everyday use. The only spec-related issues I'm thinking about are having it able to run Starcraft 2 and Diablo 3 comfortably when they come out. I'm not much of a computer guy, but if it's cheaper or makes more sense, I would consider building the computer.
If someone could basically point out a computer that's pre-built or the exact parts I need to build a computer that will run these games and perform my everyday needs otherwise for somewhere in or under the $700 range, that would be great. Also, something that will be upgradable to Windows 7 is preferred, which I think is pretty much the norm these days.