Could you write to me what is your rig scrypt setup ? I have r9 280x and I'm getting about 300 kh/s per one card. I have read that the optimal hashrate estimates about 350 kh/s. Do you know the optimal rig setup ? Here is my scrypt :

setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1

cgminer --scrypt  -o stratum+tcp://east1.us.stratum.dedicatedpool.com:3379 -u user -p password -g 1 -w 256 -I 13 --lookup-gap 2 --thread-concurrency 8193 --gpu-engine 1080

Any suggestion what I can change/add (i'm using verminer) ?