running sapphire rx nitro+ 570 8g with Hynix memory with block chain drivers, 1750 strap mod (or uber mod) but nothing gets me over 25 Mh/s and is still stable.  I have 470 8g and 480 8g cards running at 28+ all day long, but these 570 8g cards with Hynix are appearing to be crap cards.  Anyone had better luck and what have you done to get them tuned up higher.  Any core overclocking over 2000 makes the cards freeze.  Would love to hear from those that have been successful in finding a way to make these cards run at 28+.