what GPU do you have? is your GPU being bottlenecked by your CPU? if you don't know, download MSI afterburner, go to settings, monitoring, click on the things you want to monitor, then at the box below check "show in on-screen display". i would check GPU temp, FPS, mem usage and GPU usage. go play a GPU intensive game like crysis, BF3, metro 2033, etc.
if your GPU usage hangs around 80% or below, get a new CPU or overclock your 8150 or just buy a SB or IB CPU. if your GPU is 90-100% and you still have low FPS, get a new GPU. if you upgrade your GPU and it starts hanging around the 80s, overclock your CPU.