The resolution you play at will be a factor in determining whether or not your Q6600 will be a bottleneck.
Lets say you play at 1080P or below I'd say your Q6600 will bottleneck either card on both BF3 and COD, an overclock will help, most Q6600's can reach about 3.4Ghz which may not lift the bottleneck completely but should definitely give you playable FPS.
Depends on the game and depends on the resolution, generally speaking in most scenarios it wont be a huge problem.
It could limit your max FPS but then so could an i5.
BF 3 is pretty GPU dependant anyway so that game wont be an issue don't know about COD though.