Even i would vouch for a 7950 now after the release of 12.11 drivers. It not only offers better framerates than a 660-ti but always gives a better gameplay experience
by allowing post processing filters like MSAA and FXAA without much dip in performance. With a 660-ti you have to take those settings some notches down in
order to achieve playable framerates. Besides, the 192 bit bus of 660-ti takes a performance hit with highest AA settings.
So until nvidia launches some drivers which boosts performance just like 12.11 did, getting 7950 at the same price of a 660-ti is a no brainer.
You will benefit from the 384bit bus and 3gb vram while enabling highest AA settings.