I'm considering building a new hack very similar to yours, also for video post-production. I would probably vote for 1080 Ti as the video card, since it has 11Gb of memory and Resolve eats memory for breakfast, especially when things get interesting with a lot of nodes and effects. I see it as a way of future proofing the build. I've had run out of video memory previously in Resolve and with 11Gb there's much less chance of that happening.
AMD is great for FCPX, but that's it. For us - Adobe and Resolve folks - it's still CUDA for now. OpenCL implementation is just not there yet. Hopefully that will change, since if NVIDIA stops producing web drivers for OSX, we're all screwed!
After reading lots about the 8700K it seems that it's fairy simple to overclock to 5Ghz and Premiere would love that since it relies heavily on CPU speed for most tasks. So invest in a good cooling solution.
What I really would want to build for video production is a X299 build with i9-7900x (a.k.a. a proper iMac Pro alternative), but it seems that this would be a much more complicated build, not mentioning more expensive. There's one good guide here on the forums, but the tech talk there had me lost somewhere in the middle.