What resolution are you playing at?
Games usually don't utilize 4 cores, most of them won't even utilize 3. That is the reason why the i3-2120 (my precious!) could easily outperform any Athlon II X4 /Phenom II X4 in gaming. So as Vmem said, you'd be better off with an Intel DualCore G620 with 2 cores on 2.6 Ghz. I've used that one for a friend's build and it runs everything maxed up to 1440x900 with an HD 7750. Could do much more with a decent card like the GTX 560.