I'd wait for the gtx 660ti benchmark before getting a new GPU in that price range.
Nvidia state that the 660ti will have performance above a GTX580, so the gtx660ti should be place between the 7870 and 7950. That's why I'd wait for official benchmark.
It's hard to fault NVIDIA's upcoming GEFORCE GTX 660 Ti and for good reason. You're talking about a video card that is rumored to hit at the mid-$200 range yet performs like a video card priced $100 more. In this case we're talking about the HD 7950 specifically. You could argue that it can be compared against the more expensive HD 7970 at times, too.