I3 2100 + 7870. this is what I call bam.
then upgrade to sandy bridge i5/i7 in the next few years or something since after ivy it's supposed to be the end of 1155 (not sure about this)
and your 7870 should last you quite a lot as most peoples 460/480 did last them long
Too bad his budget is 350$, and the 7870 is 350..
I3-2120 for like 110 and 7850 for 250$ is the best combo imo.
The 2120 goes on sale for 15-20 off all the time, you just have to wait.