Well the 850 watt PSU exploded. The 750 PSU powered 2 of them fine.
I purchased a 1000 watt PSU and it has been running all 3 gpus overclocked for a week solid! Though thanks to this ridiculous difficulty factor increase this rig I built is not even close to being profitable.
It was worth a shot...
And that kids is why you buy decent power supplies.
Right. Two Gpu's, 850W minimum. Three Gpu's, 1200W.