Those looked a lot like the hash rates I was pushing when I first got my 7970. After some tweaking, and help from the guys in my mining pool at
www.netcodepool.org, I switched my settings to:
setx GPU_MAX_ALLOC_PERCENT 100
cgminer.exe --scrypt -o netcodepool.org:3333 -u user.name -p password --thread-concurrency 16320 --gpu-engine 1055 --gpu-memclock 1500 --no-submit-stale --intensity 13 --worksize 256 -g 2
And that jumped my 7970's into the 750 KHash/sec range everyone else seemed to be getting. Mine of course is only a single GPU atm, so you will have to make a few minor adjustments.
And I have the latest AMD drivers, and am using Sapphire TRIXX (Even though my card isn't from Sapphire) to clock the card for GPU 1055, Memory 1500 and voltage 1175.
Hope that helps.