Shini
Go Kart Champion
The 7950 is actually MUCH better than the 660, hence the price difference. It is on par with the 670. Most of the reviews and benchmarks you see are from when the 7950 first launched and had poorly optimized drivers. There was a big update since then and now the 7950 is the best "high end on a budget" card for most games, especially at higher resolutions. If I were buying a new card today I'd buy the 7950 over my 670.
Summary: 660 is adequate for decent settings, 7950 will run max settings. It is worth the extra money IF you want to spring for a better card.
660 is adequate for ultra settings on a lot of games, high settings on some of the crazy ones...Granted this is at 1920x1080, assuming that's what OP's reso will be.
If he needs the extra oomph he can do an OC on the 660 easy.
I have 660m (mobile version) and I think we all know mobile versions are way less powerful than their desktop counterparts...I haven't had any problems cranking up the settings on any of the games I play except for shadows in WoW I do have to turn those down in certain area's.