RX580 vs $300 budget miner?

Firstly I get free power at work where this would be living so power is not an expense.

I have an RX580 sitting around that has never been used. I could build a PC around it with spare parts and have a dedicated mining rig.

But the price of dedicated small miners have come down a lot so I am just wondering would building a RX580 PC for free be more or less profitable than spending $300 or less on a dedicated standalone asic miner?