I had an even weaker processor (1.8Ghz quadcore) and the same graphics (3200).
Just upgrading the graphics and PSU gave me a HUGE boost. I can run CoDWaW on full settings at a great framerate (not sure what the FPS is exactly, but there is no lag at all).
The PSU i got was a BFG 550W, which you can find for around $80. The graphic card i got is the radeon hd4770, which you can find for around $100. Also, with this graphics card, you can actually get away with buying a much weaker (and therefore cheaper) PSU, I just wanted one that would last me for many years and future upgrades.