So I have an AMD FX 8150 Eight core at 3.61 GHz CPU (never runs above 50 percent capacity). and 32 GB of RAM at 1600MHz. And I have two AMD Radeon HD 7770 series (ghost thermal version) running in crossfire mode. when I play BF3, I can play it on medium at more than 60 frames per sec. however, when I go to high or ultra settings, the frame rate slows to about 40. my question is: are my GPU's bottlenecking my CPU? should I invest in a higher end graphics card?