This is one of the baddest single card setups you can get currently. I don't care what numbers say about the i7 processors... The AMD rigs are SMOOTHER and more refined for gaming, and I have the videos to prove it. Get yourself a Dragon platform system, and you will be grinning ear to ear.
AMD Phenom II X4 965 BE (125watt) $195
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103727
GIGABYTE GA-790FXTA-UD5 AM3 AMD 790FX: $185
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128415
G.SKILL Ripjaws Series 4GB (2 x 2GB) PC3 12800 (DDR3 1600): $94
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231277
Radeon HD 5870 1GB (fastest single chip video card currently available): $410
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150443
Grand Total: $884 (before shipping)
Enjoy the $120 you just saved, and you will definitely enjoy the 200+ FPS you will be getting from this rig.
EDIT: Wow, everyone is recommending rigs with i7 920's and 6GB triple channel memory. You do all realize that the AMD platform is far cheaper and plays games just as good right? If you're dead set on recommending an intel rig, recommend a system based on the i5 750. It will be considerably cheaper, so he will be able to afford a much better video card too.