For an extra $50-$60 I'd go with an nVidia GeForce GTX 460 (in fact, here's one on TigerDirect for $125 after rebate). It is commonly considered one of the best-performing video cards on the market for the price, and it has DX11 support. I recently bought one and can vouch for it being a great performer with all of the games I've used it with: I can crank up the settings pretty high in most games.
But DuSK isn't looking for a video card anyway, so this is pretty useless isn't it?
Anyway, I'm a diehard fan of AMD processors (I personally couldn't care less for their video cards though, ironically,) so that's where my main experience comes from. If you go with AMD and want to come in under budget, you may have to sacrifice a bit and go for an AM2+ board as opposed to an AM3. I actually have an AM2+ board with an AMD Phenom X4 9750, and while it's locked and can't be overclocked, it's extremely serviceable with the games I've played: GRID, DiRT 2, Bioshock, Mass Effect 2, F1 2010, City of Heroes in Ultra Mode (which is notorious for being a CPU and GPU hog,) and some low-end games. Windows 7 also boots up startlingly fast; it's almost practically ready as soon as the desktop pops up. You might be able to go with something better since you're not looking for a graphics card or power supply, but the Phenom I will do the job.