I've got an hd 7770 with a phenom 2 x4 965 at 3,8 ghz with 4gb of ram .
In game with standard preset i've got ~ 50 fps , in low preset it's a bit less .
And when I got to ultra preset my framerate is the same than in low preset (without antialiasing or other advanced stuffs ).
So there must be a problem here .