While this is probablly not the all singing and dancing reply that you where indeed hoping for, I feel I need to inform you we require additional information to help.
Do you require extra peripherals such as Mouse and keyboard, and does a monitor need to be added to the budget?
If not, do you require hard drives? dvd writters or anything of the like?
For what it is worth, you could probablly get an:
E4300
2GB of OCUK ram
DS3 motherboard
8800 GTS
520W corsair PSU
and still be left with a bit of cash over, for hard drives and so on. A word to the wise, the E4300 is great for overclocking. I would say if you aren't wanting an E4300, to skip the other model numbers up to a E6600.
Intel rigs are the best at the moment (as you probably know). An 8800 GTX could be a tad overkill for you, depending on the resolution you play. Do you do anything else other than game. Lastly do you require an operating system?