The Sapphire Nitro+ RX 580's are great cards. Easy to mod and they get good hash while running cool. I have both the Special Edition and the non-SE Nitro+ 8GB RX 580's. I get the best performance and like the non SE (black shroud) version better since I don't like the blue LED fans that can't be turned off on the SE version. The non SE is version is also cheaper and I get slightly better performance with the non SE cards.
Great! Then I'll get that one.
I actually bought the ASRock H110, just for future proofing. Not much price difference and it was cheaper than the ASUS Z270 PRIME A.
The only thing I have to buy at another place is the PSU.
My initial idea was to have 6 GPU rigs, for load balancing (can put ~1500W per phase before I need to upgrade my incoming power). But if I can use two PSU's in one rig (didn't think about that from the beginning) then I can have more GPU's in one rig and still achieve the same result, just put the PSU's on different phases.
Lets say I want to expand to 10+ in the near future, but start with 6. Still get the 1600W for now and then add a second one when I buy the other cards?