the bottleneck in your system is your 6600 gtx.....you processor the 3rd gen i5 is capable enough to run almost all the current titles without any problem.
the games become gpu bound much much earlier than cpu bound.
A GTX 660 is a powerful card. It can handle any game at 1080p at ultra with very good fps.
So no way of Bottleneck through GPU or even CPU side.
He didn't even mention what problem he is getting.
There might be issue with powersupply.