Just figured I would add some insight to this thread,
I have a i5 6600K and a GTX1080 with 16GB of DDR4. I have my 6600K overclocked to, 4.61Ghz. I believe 93%+ of all of 6600K's can achieve a miniscule overclock of 4,680+ MHz or higher. They all overclock extremely well!
I use Sony Vegas Pro for about 4-6 hours a day. Creating, and rendering, and converting 4K videos from game play
I also use my 6600K i5 and GTX1080 for recording gameplay with Shadow play at 4K resolutions.
Sony Vegas Pro , under a heavy load, like sliding through a very large 4K video, to find a certain scene. It will push my 6600K to 50% to 100% load easily! Although, it is super SMOOTH even at 100% utilization! It handles this application with EASE! I see no need for a i7 6700K, or higher..
I am extremely satisfied with how smooth, and fast this 6600K is. Especially at 4.6+ GHz.
It is truly amazing that a Intel i5 at a very fast speed like 4.5+ GHz will handle anything needed.
I've never experienced a skip, studder, or any kind of slowdown whatsoever!
Now, graphics power on the other hand.. Well, that is a whole other story. I have a GTX1080 for a reason, it is very very heavily overclocked too. And it is not bottlenecked one bit either by my i5 6600K. GPU utilization stays at 99% in any game at 1080P or 4K.
My CPU power, and GPU power is a necessity for my everyday workloads. I could easily sell my 6600K, and upgrade to a i7 6700K for more power. But, that's a waste of time, and extra money. I simply do not need it.
If you already have a 6700K great! Its fast.
But, do not underestimate a 6600K at 4.6-4.8Ghz there just beastly.