4 cards at 150w = 600w plus mobo/cpu/risers. The 850 would be enough if you dropped the power on the cards. At 100% per card, I would go with 1000 watts.
Ok thanks for the help. I'm not sure how things will go once they are in open air. I'm thinking I'll want to push power even higher because they will run cooler. Right now I have 2 in my desktop tower and I'm limited because one runs cool and the other hotter. I'll probably just use the 1200 to be safe.
Maybe I can save the 850 for a 1060 build or something in the future.