This M520 deal under discussion has fallen through. The M520 turned out to be missing the power supply unit [PS-520] and cable, entirely. I gave the seller time to see if she could locate the ps/cable, but no luck, so I bailed off the deal.
Maybe catch this same board, less supply, back on Ebay, within a short time/TBD.
It was a good deal while it lasted, but I wanted a complete mixer that worked right out of the box./DA