I am trying to add a third switch to 2 switches already stacked. I have both PSU plugged in on the first switch and one PSU plugged into the second switch. I do have power-stacking cables attached to both. I do not have enough outlets to power the third switch. My question is can all switches run off one PSU? Also what will be the best way to stack the switches. I have 2 additional data stacking cables and 1 power stacking cable. Please advise. thanks.