Thanks!
Using: -k phatk DEVICE=0 VECTORS BFI_INT FASTLOOP=false WORKSIZE=256 AGGRESSION=13 on a single 5830 and get 312MH/sec

I have always found phatk to be slower. Why did you choose to use it? Also, why WORKSIZE=256? I have also found 128 to be faster on the 58xx and 69xx series.
I am using poclbm at the moment getting 0.2% stale rate [not using BTCMine at the moment though].
I have 7 different computers running 5830s and 256 gives about 5m more than 128. I run mine at 975 clock, 300 memory and I get about 300MH/sec.
I love these 5830s only cost $100 but can push out 300MH/sec!