Just ordered an i5 7600k as an upgrade for my Z170 build(using a locked i5 6500 now). Should be plenty of power for most gaming. However, I admit I was quite surprised in watching and reading some reviews how many modern games and other software programs utilize Hyperthreading in the i7s to boost performance. Some games show a healthy boost between the 2 CPUs. Still, being that you already own the i5 7600k, I'd stick with it and OC if it were me.