Alright buddy, what is the exact model of your card?
You should be able to get 700Kh/s+ on scrypt mining with a 7970.
I have two sapphire 7970's vapor-x ghx edition and was only getting 550Kh/s untill i did a simple BIOS flash. Now i get 730Kh/s with voltage and core speed underclocked, running at 60C.
I wrote a thread yesterday with what to do, check it out -
https://bitcointalk.org/index.php?topic=200777.0Hope this helps
Edit - I'm an idiot, i thought you said 7970
Still though, you should be able to get more than 550Kh/s and if i remember correctly a guy i helped the other day had a 7950 which i think he said he got up to 650Kh/s.