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 chose to use phatk because I saw some other posts recomend using it on 5830/5850 cards and it is faster for me by 9-10MH/sec. WORKSIZE=256 with phatk also is faster for me (by another ~4MH/sec)
Here are some results from my testing:
297MH/sec = pocldm & WORKSIZE=128
304MH/sec = pocldm & WORKSIZE=256
308MH/sec = phatk & WORKSIZE=128
312MH/sec = phatk & WORKSIZE=256
I am getting quite a few rejected blocks though, so i'm not sure if that has anything to-do with the above settings or something else.