You don't want to run PSU's close to the rated the capacity. They won't be as efficient and it will shorten it's lifespan. 50% to 80% of the rated capacity is where PSU will run most efficiently and cool. The other consideration is how many PCI-E connecors you need for all the GPU's and risers. Many PSU's less than 1000W will only have 4 PCI-E connectors per PSU. For 13 RX 570's you will need a minmum of 13 individual 8-pin connectors just for the VGA power. Some cards like the Nitro+ also have a 6-pin connector that may be optional. For risers I use 6-pin PCI-E risers only and connect two or three risers per PSU 8-pin cable using a PCI-E 8-pin to dual 6+2 splitter cable, figure another 5 PCI-E PSU ports for the risers, so in total you need a minimum of 18 PCI-E ports.
Wow thanks alot for that and everything. That has clarified alot for me. I didn't realize you have to run risers off the PCIe ports on PSUs.
You CAN run them safely via MOLEX adapters - and there are some with all 3 connections that are the recent "4 cap" versions.
The COBOC ones Newegg sells as an example, seen the same design from a few other places.
You don't HAVE to run 19 cards from the ASUS B250 Mining Pro to make it worthwhile - the on-board power supply management is nice, and saves a few $$ + is simpler vs having to use Add2PS type adapters.
If it's lower cost vs a 13-slot MB, it's DEFINITELY the better choice.
NewEgg has a Canadian branch, can't hurt to check them in addition to the other sites you mention.
I strongly recommend use of the EVGA G2 supply line over the G1 or the GQ or the G3 - the BALL BEARING fan is going to outlast the "fancy name sleeve bearing" junk in the other lines.
I'm not 100% sure on the G2L line - I think it's also ball bearing fan, but the power connections are kinda wierd and do NOT match up with anything else at all.
I can also recommend the Seasonic X-series, but those are in very short supply and getting way expensive when you CAN find them any more.
