look here --> https://litecoin.info/Mining_hardware_comparison

From what i see should get around 400khs but I'm far from an expert but maybe try this:

cgminer.exe --scrypt -o stratum+tcp://pool.com -u worker -p pass --no-submit-stale --verbose -I 18 -w 256 -g 1 --thread-concurrency 15000 --gpu-fan 85 --lookup-gap 2 --gpu-engine 1130 --gpu-memclock 1500 --gpu-powertune 20