2x Gigabyte HD7970 
my first rig (2x7970) give me 735Kh/s on W7, driver 13.1, cgminer.But secon give(2x7970) me only 570 Kh/s.
Which setting do you use?
Code:
start /D "C:\cgminer" cgminer.exe --scrypt -o coinotron.com:3334 -u Worker.1 -p x --thread-concurrency 8192 -I 13 --lookup-gap 2 --worksize 256 -g 2 -d 0 -d 1 --gpu-memclock 1600,1600 --shaders 2048 --gpu-engine 1050,1050 --gpu-fan 60,60