if you're running crysis at very high details, and very high resolution, then your cpu won't bottleneck at all. It depends on the game/rez/details. depending on those things, any cpu will bottleneck a gpu OR any gpu will bottleneck a cpu.
Well if you want you can get a GTX260 or HD4870 but that is the absolute max that you can get with a 1440x900 and Pentium E6300@2.8GHz (also try to OC this cpu)