For the PSU, I would add that only buy GOLD/PLAT/Titanium rates PSUs, these are going to be running 24/7 you want quality and efficient powersupplies
Good point. I recommend gold as a minimum. The cheapest way to power lots of rigs is to buy a small psu paired with an hp server psu. I personally have Corsair and Evga. Both have been too nice to me. They send me back new PSUs anytime I've had issues.