I just fired up my Firepro s10000 it's getting an excellent 779kH/s with stock clocks, however it has the same issue as the R9 280x's. This is in my main Ryzen 7, 16gb system, so it can't be a system issue.
Is it crashing after a while? or crash at startup? Are you on the latest adrenaline drivers? Crimson drivers have issues. Also some pools are crashing the miner more often than others. Wich pool are you using? Try the bat scripts that follow the archieve.
It isn't crashing, it throws a "failed to create verthash data buffer" code as the miner stops after donation mining, then instead of continuing with work, it does a restart where it runs through the bit of mining (like you just started the miner) then the donation mining again and rinse and repeat. So instead of you getting 1%, your getting alot more... maybe like 25% donation. It's definitely a spminer vs old 2013 Radeons issue.
Anyway, I figured something out, just run one of the Rx cards with the R9 cards and it works like it's supposed to.