To be fair, gpu is as good as irrelevant to combat arms. I only have 15% gpu usage with max settings and 1920x1200, but I get 400-600 fps. The 2600k is an excellent cpu for gaming, although with negligible improvement over the 2500k (about $100 less).
What frequency did you set the 2600k to? My 2500k seems to run faster at 4.6GHz.