I was also going nuts over my personal decision, of
AMD X2 4200, X2 4400, or the 4000 San Diego.
I finally went with the 4400. It has the most cache of the X2 models, and can be overclocked past the 4800(2.4Ghz) easily.
I also went with the X2 because its the future... not really that I need that much, the overclocked 4000SanD probably could handle everything im doing now.
Music, messengers, photoediting, gaming, downloading, browsing, and webdesign.
It helps having X2 if im doing a few of those at once. Hope this helped you as someone who struggled the same decision.