The 600 with LTC is a totally different quantity. It's 600K vs 300M. 600K on scrypt is actually pretty poor for a 7950, with proper overclocking and the optimized kernal by Lantis I get 670-705, depending on how high I can clock each card.
Ed
I'll look into that If I go back too ltc at some point. I was using guiminer so thats pry why I was low