I'd recommend either the i5 7600k, or a Ryzen 5 1600x. With that i5, you'll want a Z270 board, and with the Ryzen, an X370. Both these systems are very well paired with your card, and will actually allow headroom for upgrading your CPU later for newer, better cards. In fact, I'd personally say the 1600x, just for the reason of upgradability alone, not including the fantastic multi-core benefits, and *hyper-threading* that whips Intel back into the corner. The AM4 socket is in the infantile stages; whereas LGA1151 and LGA2011v3 are on the way towards the door, given Intel's generational history with their socket types.
TL;DR: Ryzen 5, which is about 10 bucks more expensive than i5 7600k.