I can actually get a little over 700kh/s on my Powercolor without flashing it
use the mem and clock tuning in cgminer and set it to 1020/1450
and i use the same config in scrypt as you do
heres some info on the card i have
if you like i can send a copy of my bios..
PowerColor Card
GpU-Z
015.032.000.002.000000 (113-C3860100-100)
Tahiti indentifier- HD 7970 (SK Hynix H5GQ2H24AFR)
you have the AFR vram which according to The Stilt has the correct timing built in. I got the MFR which is the rubbish timing. But I already got a modded bios which can get me 750KHs so I'm good! But thanks.