I seriously cannot believe this worked I have 2x XFX 7970 GHz Edition cards that I couldn't push past 575 khash/sec @ 1100 / 1800 MHz, and that was using 650 watts (measured at the wall)...
Just flashed that Gigabyte BIOS mentioned earlier, the 925 MHz core version and now hit ~650 khash/sec on each card, @ 925 / 1500 MHz and am only 450 watts!!
Better yet, I have a custom water loop that was running "hot" at 55C earlier, now it's stable at 40C and I'm speechless. Incredible, goes to show that hardware performance truly is all about the software
Thanks for all the hard work OP, and research by everyone in this thread!