The question is: What games do you want to run, and will you be running in the near future?
Your looking at about +10-15 more FPS for a "newer" single video card solution. I personally wouldn't upgrade, but I'm always broke. Is that performance gain worth the money to you?
For gaming, a i7 is useless (no games will use all the cores). The i5 2500K is everything you could want for games. If your building a new PC, go ivy bridge. :-)
This should bring you up to speed...