One, don't use a case. Look at how miners mounted their hardware on racks and take notes. Cheaper, better for temps, and the most efficient use of space.<p>Two, I recommend ignoring electricity cost and using all you can. If it's cheaper now than it ever will be, use it while it's cheap. If it will go down due to renewables, nuclear, etc in the future, it's good to buy up the GPUs while their price is artificially depressed from energy fears.<p>Third, go for server type PSUs and breakout boards. The server PSUs cant be beaten in watts for your dollar, and are extremely efficient.<p>Finally, consider scooping up some x79 and x99 xeon boards from Chinese sellers. They're cheap as hell, have PCI lanes out the wazoo, etc. This means you don't have to fool with as many mobos to run the same amount of gpus. If you go this route, don't get the bottom of the barrel no-name motherboards. Machinist is a decent one.