I think zonet's idea is good..
I'm going to be playing:
C.O.D MW 2 and 4 if i get a new CPU
Far Cry 2
Will work good but the rest wont. A Q6600 will have so much hard time on COD Black Ops even at 3.2Ghz. The worst is GTA4 since the game is coded really bad.
But you can't really say you'll play only those games. When BF3 came out and I saw the trailer I have to change my PC but budget problems.