If you can wait, go for Ivy Bridge (April 29th), and get the i5-3750k ($220), and the Extreme4 Z77 ASRock mobo ($150). If possible, upgrade to a 7850 with your GPU, as well. Make sure you get a CPU cooler! Hyper 212 is great!
I'd definitely say get the 7850 for your GPU - the 7870 is great. Whether you want to wait for Ivy Bridge or not is up to you - you won't notice much if any difference in the CPU and RAM, but you will notice it in the GPU, but the 7850 isn't Gen 3 - it's only the higher end ones that are.