I'm an active member of another forum and there is a lot of info on steppings. If you tell me which AMD chips you're interested in I could most likely answer your question. As for the Opteron 165, the CCB1E stepping is pretty good and it should clock to about 2.7 on stock voltage, and 2.8 at around 1.55 vcore. Some people have theirs up to 3GHz but then again they are usually on water or phase-change. Once you start hitting 2.8 on Air (even with a lapped ThermalTake Big Typhoon) you're pretty much limited by temp. Also, the CCBBE stepping is pretty good but I think it runs a bit hotter. I'm pretty sure it's a better stepping for water/phase overclocking, though.
What other chips are you interested in?