The PSU is an overkill. I doubt these GPUs can drain more than 600w under full load along with all the other components. But yeah you can always sell em later and invest the money you mined into 1070. 1070 is a monster for ZCash mining. ETH too, I've seen 32MH/s on a card on youtube, then your 1000w PSU wont be an overkill. All in all, I couldn't get the 6th GPU to load. At first my PC wouldn't start and I had to do various configuration in BIOS, disable and modify lots of options... If you can help me get the 6th GPU running you can. However I will be looking on a fix online for today, I was very busy yesterday getting the rig to run and got tierd. So my job for today is to get the 6th GPU to run, and see whats the max OC i can get with them.