A8 6600K is 3.9ghz. Hypothetically, if it's limiting you to 30fps in a situation, if you overclock it ~25% to 5ghz, you might get a 25% framerate increase in a CPU-limited situation. 25% more than 30fps is 37.5fps.
A 5ghz OC is pretty extreme for these CPUs.
Whether or not you'll have a bottleneck will really depend on the game, and you'll have to look at benchmarks for each, but the A8 is low-end enough that I expect you'll find it's the limiting factor in some games, but not in others.