Just got to use this with my r9 280x and love it!! Getting about 200 sol/s.
Old 280x cards with claymore's miner(and I think with optiminer's miner too) can show more better results - up to 325 sol/s with modded timings.
It's true. With 12.5 Claymore I have on my 280X 330-335 Sol/s with modded bios, overclocked memory and downvolted core.
Optiminer gives only 275-300 Sol/s.
For anyone still following this I did endup finishing with 1075core/1500mem and undervolting to 1.021v (Stock for 1030core is 1.2v). Averaging 320sol/s. Intensity 6!!! Intensity 7 requires more than 3gb ram on card. I cant complain about temp being 66c with fans on 30%. My r9 has Samsung memory and no matter what mem clock I tried the sol/s decreased. Cheers... maybe next I'll try excavator.
This card is PowerColor TurboDuo R9 280X OC