Best settings for mining using an Asus HD7950 OC Direct CU II

[ZARious]

I've got an Asus HD7950 OC Direct CU II, and I'm only getting about 550kh/s mining Litecoin - from what I've seen, I should be seeing more like 650+?

I've played around with the mining settings, so far the fastest speed I can get is using the defaults from GUIMiner-scrypt for the 7950. I'm going to change over to using cgminer directly (I've read you can get better performance / more flexibility) - what else can others suggest?

What I can say about this card is that it runs very, very cool in comparison with my other cards (Stock 5870 / Club3d 6790 / Club3d 6850).