DJDeCiBeL :
You can absolutely use a PCIe 3.0 card, it would just run at 2.0 speed, but that's not even anything you should worry about. PCIe 3.0 only really makes a difference when you go Tri and Quad SLI/CF.
right, and even then its only a penalty of a few percentage points.
OP, I would personally go with either the i7-3770k or the Ivy Bridge i5. If your primary purpose is to game on your PC, the i5 will more than suffice and is a really good processor for the money. The Ivy Bridge i5s and i7s do run hotter when you get a certain point (Over 4 Ghz, iirc) but are faster than the sandy bridge based processors at the same clocks and use less power. If the "old" gen of processors are the same price as the new tech, I would go with the new tech most of the time. Also, it is a really good idea to run your memory at 1.5v or less, as has been previously stated. I remember reading something about higher voltage memory (more than 1.5v) causing degradation of the IMC and chip over time.
When you get down to it though I would be more than happy with either generation of i7s or i5s. Sorry if I rambled; its late here.