you don't need 2 motherboards.
and that is massive overkill. you don't need a 1200W power supply for a system that will rarely break 300W, and probably max out at 450W fully overclocked, a 600W psu is all you'll need, unless you plan on getting a 2nd gpu for SLi at some point. in which case i'd get a 800W psu and call it a day.
you need a cpu cooler, skylake doesn't come with them, and it's a hard cpu to cool due to heat density and bad TIM. so... i'd get something robust as a cpu cooler like a h80i or if noise is a concern, something like a Swiftech H220-X, or, keeping with your black/white theme something like this
Phantex PH-TC14PE
Finally, fallout4 doesn't run smooth on any system or any settings. it's a critically bugged mess. it will not run on this system in 4k smoothly. just keep that in mind. the GTX980ti is a nice gpu, but it still isn't able to max 4k, you'd probably need a 2nd one for SLi to max most/many games in 4k.