An i5 is plenty...depending on your budget and overclocking needs I would strongly suggest something along the i5-4690k
What sort of budget are you looking at? And what sort of GPU setup are you considering? If you just want to use a single GPU, and no overclocking, then that would mean a different motherboard. Of course wanting the option to either Crossfire or SLI (or do them both), that also matters a lot.