I have 6 x MSI R9 390 with PRO BTC H81 and Powered ribbon risers (unpowered)
from what i know you need 2 x1200w PSU and something like 600w PSU for the Mobo!
I wish you all the best with your set up and driver install etc.. its gonna be a nightmare.. take it from me
I have a total of 30 x MSI R9 390 cards and 5 PRO BTC H81 Mobos. i only managed to get one of the rigs running as it should.. and that is without any OC.. because afterburner is not allowing asrock motherboard or Intel shipset...I guess they prefer us to buy MSI Mobos... so its all crap :-/
Let me now if you have you managed to configure your set up.. looking forward to that :-)