I am watching the overclocking results ppl are getting at Xtreme Systems in the AMD forums. Some are approaching 4gz on air. 3.7 - 3.8 seems to getting common. I was going to get one to upgrade this system but now am considering a new system for a PH2 and using this one on the TV for video.
Dunno what you are getting out of your 9850 but if I could get another 800mz I would be happy. Even 600 would not be too shabby.
It really depends on your clock. Currently, I have both an 9850BE AND a 940BE. I don't know about the 920.
The current everyday clock I run the 9850BE at is 3.26Ghz, but I have had it as high as 3.48Ghz on an Asus M3A32-MVP. I am sure I could get the 9850BE stable closer to the 3.48 mark, but I havn't had time to tinker with it more.
As for the 940BE, I'm running it @3.62Ghz stable on an Asus M3A79-T. I've had this cpu up to over 3.8Ghz, but once again, I havn't had time to see exactly how much I can get out of it.
Anyway, clock for clock the Phenom2 is faster than the original Phenom. How much ? Depends on what you do, what programs you run etc, etc.... My daily rig is the 9850BE with 2 VisionTek 4850's and a 22" monitor. It screams and does everything I need it to do. The 940 is the new LAN rig.
IMO, since Newegg dropped the price of the 940BE to $235, I'd go with the 940 over the 920.