Re: which one?
I would think so. The Athlon 64 3500+ is a good decent CPU, but I feel the dual core is even better. If you're the type of person that runs apps all day, game, and surf a lot on the web, the X2 is a great CPU to get. It's an all around good CPU.
The 3500+ is just as capable too, but it can eventually bog down on you when performing a significant amount of multtasking and encoding. With dual core, you're ready for the future. More and more apps and games will be using dual core soon making it faster and more efficient. They keyword is efficiency which results in performance boost.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?