+1 phenom II solution. You just aren't gonna get a lot more outta that processor. I wouldn't do any more overclocking with the stock heatsink. you may get another 100Mhz with a beefier air cooler. So you would have to decide if another 100 Mhz or so is worth 35-40 bucks.
I personally don't recommend anything below 2.4 Ghz processors for modern games, although if frame rates in crysis are what you're after prolly nothing less than 2.8ghz. But really, crysis is a system killer and if you wanna impress someone or yourself with frame rates you should look at a top end video cards.