Which processor would you have chosen for this build?
And to answer your question, if it was just for gaming probably a ryzen 1400 or 1600 and overclock to 3.9ghz (no bottleneck on any GPU 1060 or below, and hugely powerful at multithreaded stuff at a low price).
Gtx 1080 & 1080ti I would go for you your chip (8600k) or the i7 8700k. The 1070 it would depend on my budget. I hope this makes senses!