I think the build is pretty good but you can get another mobo for this non-K processor.
You mentioned that you want to run AAA games at 4k/60fps. You can get a 1080Ti instead of a 1080 (or just wait a little longer for the new NVIDIA GPUs) for better 4k performance but, it's still not really enough for a stable 60fps on most AAA games, I believe, without lowering the graphics settings.