get the i5 3570K (no difference in gaming, really) and get with that extra 100 a 670.
now, while I just suggest a 670, that's because you started off with an Nvidia card. I personally think AMD GPUs are better, and the benchmarks done by this site generally agree (and they're cheaper) you could get a 7950, which overclocks well and can easily outstrip a 670.
what's the site you're ordering from, and I'll put a build together.