Do think a 850w gold power supply rated at 70A on 12v will be able to handle the C1? I know it will run at 100% capacity but I have no use for it otherwise.
cutting it REALLY close - good chance you'll have to underclock in order to run stable, especially if the coolant pump draws an extra ~20w. IMO get a 1000W PSU and youll be fine, and your efficiency will be a bit better (most gold PSUs are ~91% efficient at 80% load, but only ~85% efficient at 100% load)