Alienware's are pretty good too.
Heres the cheapest alienware desktop : Alienware Aurora Desktop Details | Dell
You can also customize the computer after you have selected it, and to see what processors & graphics card are good for you, check out this website : Game-Debate.com
I built a pretty good PC for 1,499$, the GPU Isn't best available but better than the one I'm using now
So if you have time to compare the hardware I recommend AlienWare/HP, just google and you'll find good websites.