Keep in mind you want a dual mini 6 pin to 8 pin power adapter as the RX580s have asymmetrical power draw.
You can probably find that card easily in the $130 - $150 range, used. Don't waste the money on a MacVidCards flashed card. I have found it has not been a problem for myself. 580s, Vegas, Radeon VII (what I run), and 5xxx series all work.
There's also a great Mac Rumors thread about GPU compatibility as well, unfortunately I couldn't quickly find it to let you know.Īs far as cMP goes.