1. For a top end build, that will run multithreaded apps, I would pay a bit more for a I7-6800K.
It is a more power efficient 14nm processor vs 22nm for the 5800K.
2. Photoshop can use lots of ram for workfile.
Consider buying a 32gb kit. Dominator is a marketing brand; I would use the lpx variant with no difference in performance.
3. The motherboard supports M.2 pcie x4. Use a Samsung 950 PRO m.2 ssd.
4. 750w is minimum for sli GTX1080
I have no problem overprovisioning a PSU a bit. Say 20%.
It will run cooler, quieter, and more efficiently in the middle third of it's range.
A PSU will only use the wattage demanded of it, regardless of it's max capability.
5. Seagate may not be your best hard drive option for reliability.
WD is likely better.
Read up on the WD rainbow.
https://www.pugetsystems.com/labs/articles/Understanding-the-WD-Rainbow-674/
6. Lastly, a good noctua cooler like the NH-U14s will do the job better and quieter.
My canned rant on liquid cooling:
------------------------start of rant-------------------
You buy a liquid cooler to be able to extract an extra multiplier or two out of your OC.
How much do you really need?
I do not much like all in one liquid coolers when a good air cooler like a Noctua or phanteks can do the job just as well.
A liquid cooler will be expensive, noisy, less reliable, and will not cool any better
in a well ventilated case.
Liquid cooling is really air cooling, it just puts the heat exchange in a different place.
The orientation of the radiator will cause a problem.
If you orient it to take in cool air from the outside, you will cool the cpu better, but the hot air then circulates inside the case heating up the graphics card and motherboard.
If you orient it to exhaust(which I think is better) , then your cpu cooling will be less effective because it uses pre heated case air.
And... I have read too many tales of woe when a liquid cooler leaks.
google "H100 leak"
-----------------------end of rant--------------------------
Your pc will be quieter, more reliable, and will be cooled equally well with a decent air cooler.