Proper answers from maziar.
To assess your performance improvement potential, run this test:
Run your games, but reduce the resolution and eye candy to a minimum. This will simulate what will happen if you upgrade to a stronger graphics card. If your FPS improves, it indicates that your cpu is capable of driving a stronger graphics card to higher levels of FPS.
I think your cpu will be OK as it is. To assess the capability of your cpu, run this test:
Keeping your graphics resolution and settings the same, reduce your cpu power. Do this by removing the overclock, or by using windows power management to set a maximum cpu% of perhaps 70%. If your FPS drops significantly, it indicates that your current cpu is a limiting factor, and that a faster cpu or overclocking would help.