If gaming is a big priority, save money on the CPU and instead focus more attention to the GPU. The 8800gs or 9600gt, when running Crysis, are both outmatched by the 8800gt 512mb, which would be fine with that 450W corsair PSU. The E2 series, as mentioned by redmo0n, is where I'd look to as well if you're wanting to remain in budget or as close to as possible.
I hate recommending parts that are more pricey than what people want to spend. I really do, and for that, I'm sorry, but all I'm saying is that if you're aiming to game on this system and expect to turn on some eye candy, especially with Crysis, you're going to be so glad you spent the extra money on the GPU. After all, the 8800gt 512mb version cards compare within a 3% margin in many tests with the 8800GTX series, which is HIGH quality and quite pricey, but for a fraction of the cost, and use less power