I might take your CPU + Mobo combo.
As for overclocking, I haven't decided yet. If my cooling is decent and I can do it safely then I think I might.
Two words: Price projection. If I know how much it's going to cost me, then I can adjust how I spend money to save for a huge purchase like this.
Edit: another alternative. Would I be better suited cost-wise to buy a better graphics card and put it in my stock computer, or would my crappy processor/cooling prevent it from operating at it's peak performance. Or, at least, not make any noticeable difference in-game.
A bit late on this and yes. If you bought a new graphics card and put it in a stuff computer it would definitely be bottlenecked. If it's a namebrand computer than the manufacturer had probably made it so you can't expand it's capabilities very well.
I would highly recommend building a computer. But hey, whatever floats your boat.