Thought I should do my due dilligence and post on this...
I *had* 3 XFX 7970 GHz Edition 1050/1500 Double Disappointment cards (I've RMA'd them back to the depths of hell whence they came, and got 4 x 7950's instead...).
I couldn't get them to mine LTC above 550KH/s. Ever. I tried everything.
For BTC, however, after lurking in these forums for a while, and tweaking/overclocking, I found the following to give me 675-700MH/s per card. Here was the .bat file I kept in my cgminer folder, and then shortcut to desktop/startup:
color 02
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer.exe -o stratum+tcp://MINING_POOL_URL:3333 -u WORKERNAME -p WORKERPW --shaders 2048 --intensity 13 --thread-concurrency 8192 --gpu-engine 1100 --gpu-memclock 600 --worksize 256 -g 1
-g 1 is for 1 card... change this to however many cards you have.