Well, on Watch Dogs with VSync off I get average 40 fps with everything ultra except the texture setting that require 4 gigs of vram since I got the 2 gig version.
You can compare the cards at this link below:
http://www.hwcompare.com/14813/gefor...adeon-hd-7950/
Better to go with the new GTX 970 or 980 though. Uses way less current and performs better at stock:
http://www.hwcompare.com/18063/gefor...adeon-hd-7950/