I have MSI Armor Oc rx570's with 4gb Elpida Memory.
I modded my bios with the 1500 Straps, undervolted to 900mv, TDP 75w, max power limit 100w. Afterburner settings to -57mv, +15% power limit, 1128 core clock, 1750 mem. They were hashing at 25-26 MH/s each with 88w at the wall each mining ETH. One runs on the radeon mining drivers, the other doesn't (setup on two different computers). I think the 570's are a bit tempermental compared to the 470's. Not sure about the 580's.
You really need to mod the bios to get a better Hash rate to power consumption ratio. For me I would rather hash at 26 MH/s at 88w compared to 28 MH/s at 150w. @88w at the wall, the fans only run at like 25% so they are very quiet for in-house mining. They operate at 56C right now. Currently I'm mining on cryptonight algo at 735-740 H/s using the same bios setup because I was too lazy to reflash

1268 core, 1750 mem, 87-88w @ the wall.