Yeah, better CPU I find preforms better in games. I have a old crappy 7300 GS but after going from a E4400 @ 2ghz to E8400 cranked to 4.3 I can now play that old Simcity 4 game on highest settings. Before I could only play on med
Your mobo pwns mine. XD I'm on an asus p5q
Try setting multiplier to 9 and bus speed to 450 x 9. There, that gives you 4.05Ghz. I don't think you'll have a problem getting there, taking it that you have a decent heatsink other than the stock cooler.
As you go higher up (increasing bus speed) you might have to raise the voltage little by little. Test, and see how it goes. Remember, more voltage = more heat, so don't add voltage you don't need.
(following all using 9x multiplier)
470 bus speed = 4.2Ghz
480 = 4.32Ghz
490 = 4.4Ghz
500 = 4.5Ghz
510 = 4.59Ghz
520 = 4.68Ghz
530 = 4.77Ghz