I want to join this topic since I own 3x R9 280X Sapphire Vapour-X purchased in late december 2013. All configs I've tried (including from this topic) gives low kH/s in range 400-570. However I've managed to obtain quite stable 700-704kH/s for each card.
Settings I'm running now:
--gpu-engine 1080 --gpu-memclock 1500 -I 20 -g 1 -w 256 --thread-concurrency 24000 --gpu-powertune -20 --temp-target 70 --auto-fan
All 3 cards gives the same kH, however, gpu's are 68,68,75C and fans: 50,71,100%, respectively.
I don't know how to check bios version or VRM temp because I'm running my rig on Debian (anyone knows?). Also don't know if I have elpida or hynix on cards.