1) no --thread-concurrency or --worksize switches in your config?
2) the 7950 has a core stock frequency of 925Mhz (at least my Sapphire card does), so you're quite a bit overclocked there at 1055. Not sure why you're saying the KH you're getting is at "stock" clocks. Or were you referring to your 280X?
Yeah, I only meant stock clocks on the 280Xs. And the point of xintensity is that you don't use thread concurrency. It's used as a multiple of shaders.
Oops, I misspoke. xintensity and thread-concurrency aren't (I think) interrelated. But no, I didn't specify either thread-concurrency or worksize and cgminer appears to have figured them to be 8192 for 280Xs and 8960 for 7950s, and 256 worksize for both.