well, if you are using it mainly for gaming, get the 1070. Huge performance boost over the 1060.
Adding a couple hundred Mhz cpu speed wont have an effect in that many games and will be minuscule compared to the performance gain from the better GPU
Wait 2-3 weeks till the Z270 series drops and then the price of Z170 boards will tumble and take the 6600k down a notch. In addition, the 1080Ti will also knock down the price of the 1080 and 1070