Try this:

worksize 128 (or 256)
aggression 17 (may be 19 - often DEATH)
sharethreads 8
threads_per_gpu 1
lookup_gap 2
gpu_thread_concurrency 3200 (or 3100)

And gpu core overclock to 910-960
my 5770 (910 ) give at 207-210 khs per sec.
Edit: need more than 1-2 gigabytes of RAM computer