Old thread, but R9 390 are are doing very bad these days 26mhs thanks to tlb bug.
Yes with the R9 290 its even worse. I think I got 29MH/s with the stock clock settings on (947/1250) with Stilt bios. Now it gets less than 25MH/s and despite the speed decrease the power consumption more or less remains the same and hence its no longer profitable to mine with those GPUs.
Surprisingly they still hold a decent value for gamers and are selling on eBay for fair prices. Will most likely be putting mine up for auction soon. Highly doubt AMD will release a fix for the Hawaii chipsets.