For me 280x have been doing 500h/s and the better one 550h/s on claymores, 290x at 840 h/s at total of 850W, with xmrig 280x are doing 460h/s, the best one is 500h/s and 290x at 790h/s. total usage 960W
I lost about 280H/s in total, and power consumption is 110W higher. Is there any better miner for 280x/290x?