You should be able to get 800+ on those cards each.
settings, please? I can't get over 740 with mine, MSI has been a much better performer for me than sapphire dual-x or gigabyte windforce
800+ is impossible. My elcheapo MSI 280X only gets 688kH, because it's crappy core only does 980MHz stable. 720kH is the normal top-end speed of these cards, 800kH is a drug-induced hallucination.