Order of importance for a gaming rig these days:
1. Graphics Card(s)
Find what resolutions you're going to play at, and what settings are important to you. Also include your budget.
If you have a budget, spend the least amount of money on a CPU/MB, then the cooling situation (your case), then they type of monitor (if you need one), and finally, save around $110 and see what you can find for a graphics card.
You don't want to waste money on a CPU/MB as will barely affect your gaming experience. I played on an i3 2100 (dual core) at stock and a 1090T (hexacore) at 4.0GHz, and an i7 920 at 4.0GHz (quad core), and they're all roughly around the same price these days (if you buy used). The only thing different was Minimum FPS, and that was only a 1-4FPS difference.