the only big problem i see is the seagate 3tb hdd, it has a very high failure rate. many 3tb drives do, so you might want to switch to 2tb or 4tb. if the hdd is for backups or important storage, you might want to consider an enterprise hdd for reliability. i would also look at the noctua d15S vs the d14. if you plan on doing any overclocking and having the option of adding a second gpu, you might want to get a higher watt psu.
the gtx 1060 6gb is more common with the 6 core cpu, so you must be doing something extra to be considering the gtx 1070 and 1080...
once overclocked the 6 core cpu's perform close enough to negate the price difference, so it comes down to 28 vs 40 lanes. you mention adding a second gpu as a possible option, but not a certainty... depending on what other hardware you plan on adding, the 28 lane cpu 5820k or 6800k can still run multiple devices and video cards. 28 lanes with that motherboard can be split to x16/x8 or x8/x8/x8 for pcie slots. depending on the gpu usage and program, the gtx 1070 might loose a little performance dropping to x8 or it might not. not all software and plugins support multiple gpu's, so depending on the software you are using replacing the gtx 1070 with a faster next gen single card might also be a better option and also remove the need for the 40 lane cpu. that extra money saved from the 28 lane cpu can then be spent on upgrading things like storage, psu, and case etc... if your active projects are small enough a samsung pcie m.2 ssd might be fast enough to hold everything (os/apps/cache/projects/media) and then move finished projects to the hdd. the 950 pro is around $340 and the 960 evo msrp is $250 vs the $160 of the 850 evo it would replace in your build. the 960 evo isn't out yet and i haven't seen any benchmarks to see how it compares against the 950 pro.