I have a Athlon x4 640 3.0ghz. With a 650 ti boost sc 1gb. When i play bf3 on a 64p server it drops to about 10-25fps. When i play campaign or on a 32p server i get 50-70fps, high settings. Crysis 2, 30-50fps one level from maxed out settings. minecraft, 80-110fps. So with cpu demanding games there will be bottlenecking, but its not bad.
edit: going over the specs again, that cpu is quite better than mine. Is the 660 a 660ti or regular?