What editing software will you be running with? Compatibility in parts matters quite a bit in overall performance. You can beef up the components all you like, but if the parts aren't compatible with the software you plan on editing with, a lot of performance will be lost. Make sure you take this into consideration. Because the biggest isnt always the best, or most efficient for your specific needs.
For example the build you put together is not recommended for Adobe Premiere Pro. Not that it won't work in permiere. But when you start to apply multiple transitions, or stabilizers, or color coding, etc the 'smooth' playback capabilities all the sudden become choppy, and require specific additional rendering. The i7 with a SSD and a gtx 1080 is top of the line and you would think it would laugh at that somewhat simple process. But because premiere doesn't reccommend using the 1080, it doesn't mesh well and you can run into issues.
As far as simple playback on very basic editing: I believe the system you put together will easily handle raw 4k smoothly in the timeline. But once those more advanced edits come into play, the system will still have some issues that will have you beating your head into a wall.
Ideally, id also reccommend going with the i7 7700k, because it is the same price as the 6700k. Also look to move up to 32gb of ram in the future, and additionally a 1T SSD minimum for handling 4k work flow daily.
