But you want a Z170 board to take advantage of the 'k' unlocked status otherwise its a pointless swap
So buying a 6700K. I would also need to buy a new motherboard to take advantage of the new CPU?
Yes and no. The 6700k will also work in your current board with the 6700 non-K. But chances are you got a H-series motherboard. These are for non-K (no overclocking) CPUs. To OC a K-CPU you'll need a Z-series motherboard.
But in my opinion that upgrade isn't worth it at all.