Eh not to bag on it too much, but you might be thinking of the 660ti (which is good), not the 660 (which is okay).
http://www.anandtech.com/bench/Product/550?vs=660
The 7950 handily beats a 660, but is similar (worse or better by ~10% depending on the game) than a 660ti.
Either way, still good, but solidly mid-range, while I'd call a 7950/660Ti mid-high.