the cpu score of the gtx's is more than 2 times as much. But still the 3870x2 is faster. cause one sm2 its 35-40% more powerfull and in sm3 its more like a 85-90% wich is realy impressive.

If you pair this beast up with a york @ 4.5(wich is do-able on air) you'd have a nice 24/7 game rig.