Should I upgrade my GPU or CPU? ... Many games now use more cores as a matter of course (the quad-core CPU seems to be the most prevalent), and thus experience faster and better FPS rates. So you'll probably want to go with the slightly higher-priced quad-core processors if they're not too prohibitively expensive.

Does changing CPU affect FPS?

Typically yes, if you upgrade your CPU to a more powerful, newer model it should also improve the performance and FPS. However, how much it increases your FPS entirely depends on your current CPU and which CPU you're planning on upgrading to.

What upgrades increase FPS?

Adding RAM can give you a significant FPS boost, though not as much as upgrading your GPU or CPU. Still, if you can afford the new RAM, it won't hurt.