Thought I would post this as it may help some people out.
i5 2500K 4.6GHz
HD6950 in crossfire
13.2 Beta 6
Seemed to be having an issue with low GPU useage limiting frames and offering worse gameplay than otherwise could be had.
Ran Dxtory. Started recording gameplay. GPUs kickstart to 95% load and the good part is they stay there when recording is stopped. Giving ~30fps more and making good use of a 120Hz monitor.
Give it a go if your cards arnt making full use of their GPUs.
Cheers.