I've been reading a lot here about people being able to run 4 GPU fine and the 5th GPU hosing things up.
I was hoping to finalize a 6 RX580 GPU rig this weekend based on the GA-Z270-D3 motherboard. Currently it is doing great with 4 of the 6 GPU's in. http://368720.ethosdistro.com/
I'm waiting on the last 2 GPU to arrive. Making anxious to see if this will sink or swim as a 6 GPU setup.
We have 16 inches of snow today, so I'm staying home waiting for shipment. :-)