[RayW]

Don't look at CPU speed alone. A 3.8GHz Pentium 4 will not be anywhere near as fast as a 2.8GHz Core i7 CPU. You need to look at the CPU itself which is the most important. Anything from the first-gen Nahalem to the latest 4th generation Haswell i7 and i5 CPU's will run pretty much any game fine, even the ones with the lower clock speeds. I'd be more concerned about the GPU.