The thing I noticed when you simply move up from a 2.0ghz cpu on even an older Socket A board to a 2.2ghz model is that you will notice the immediate difference. I went through 3 models on the last build and currently looking for a second on the present. Even the 3800+ X2 2.0ghz model would be a step up being a dual core model as well.
For multitasking and video capturing that would even work better then moving up to the 3500+, 3700+, or 3800+ single core model. The 4200+ was advised in the sticky for being a good dual core model for gamers who want to oc. For the Opterons the 165 was the ocer while the 180 or 185 looked at here for multitasking would be premium. The model you decide depending on budget as well should match the application. Gaming needs performance, work horse needs multasking, and simple desktops run...? "anything"! within the budget planned anyways.
The reference made by Cromewell on the 4200+ works for being the big step in two things. Besides a faster model you also get the increase seen for multitasking with a dual core model. The X2 series is meant to be the "work horse for desktops" type model while the Opterons are geared more towards server type cases. The FX is the gamer's dream while having only one dual core model. The Atholons were meant for average and not elaborate.