"Its 939. They stopped making 939 processors and are moving on to am2. "
- I'd like to see where you got this imformation from, I honestly didn't know they stopped makeing them.
A 4800+ is a great proc, don't listen to them. That's more then enough CPU then you need and will need for awhile. And you should of picked up anything in the 7 series over the 6.
You don't need AM2 unless you want to use DDR2 mem. And at this point in time, you don't really benefit from it. If you want to build a computer and "future" proof it, in a way, and want to be able to upgrade to DDR2, then you'd want to get AM2.