if i were you id save some money on the cpu and put more into the gpu and get a 6850. you may want to look at a phenom x4 965 or core i3 2100 to save some money there. they are both very capable CPU's for games. AMD motherboards can be had cheaper also. I stongly suggest you find a way to fit the 6850 into your budget.
My Main point of the PC is not to game, It's to do everything including some video editing and basically everything. So I've figured that a Intel i5 would benefit then a gpu when im doing everything in one. If i do get the i3 though, i'd get the 8GB but i don't really need it.