Firstly, good luck finding 7x RX 580s. They are out of stock globally.
We shall see, I've placed an order with a vendor... they claim they'll be ready to ship in 15 working days... which, while not what I'd prefer, gives me time to get everything else ready to rumble.
Second, if you undervolt, you can get your cards way under 225w. Personally, my RX 580s run between 60w-100w for eth only mining. Dual mining can be +50%.
Also, you generally want to run your power supplies at only 80% of their max if mining 24/7. If you constantly run it at 90%+ of load, then the lifespan will be significantly reduced.
Good info there...
I like the idea of using a server power supply... much more cost effective than the high end desktop PSUs. I'll do some shopping around to see if I can find something. Good advice!
Thank you for the great info!