Oops, true, sorry about the wrong section.

In fact, I own a R9 390, the part I have right now. And I am considering buying two RX 580. (The other option was to buy more R9 390 but I have a better buy opportunity with RX 580 and it also sounds more profitable)

Glad to hear I can mix up those. Still can you tell me a bit more about how to manage the driver then? (or others things I would have to manage in this case)
Can I just instal both drivers and it will automaticly be ok? Because I don't think I am in a "one driver for both cards" scenario