Transmissions are the primary concern with 8th generation 06 to 11 Impalas - especially the SS models (made from 06-09). They are fun cars and a tremendous used car buy IMO, but factor in buying a new transmission when calculating how much you want to spend/can afford. The 2012s, though still "8th gens" have a superior 6 speed tranny (and the 3.6 V6 making almost as much power as the 06-09 SS).