I just recently upgraded from a GTX 285 to a MSI 7870 HAWK. However, when playing the same games on the same settings, the 7870 actually performs worse, and lags in a few games like NFS Most Wanted. Or perhaps its a CPU or PSU bottleneck?
i7 920 @ 2.67 GHz
12 GB DDR3
750w PSU (I think it could be my PSU as its a old, no name brand)