Hashrates using the silentarmy v2 kernel:
R9 Fury X @1050/500 - 35-40 Sol/s
R9 290 & 390 @ 1060/1500 - 32-34 Sol/s
R9 280x @ 957/1200 - 28-32 Sol/s
Overall I'm really happy with the performance, but fixing the stability so it doesn't crash every time would make it even better

I have 5x 280x cards. When you say 957/1200, does that mean Core/Mem? Have you modified your actual rom file to those numbers and then flashed your bios with ATI flash or does 957/1200 mean something different and something you can set in windows? If it is something different, can you tell me how to set those numbers? I want to try your settings on my 280x cards. Thanks!
The card is underclocked. using afterburner.