You should definitely try cgminer. Go along the analytical readme and most likely you will be able to squeeze out more Kh/s from your cards
Using a neat program called "cgEasy" My miner is running on with default settings at dismal ~ 200Kh/s. The rate is slower to climb it's max than guiminer. I will attempt to modify the .bat and "optimize" it for my setup (multiple and mixed gpus)