I would look more into the Dual core area.
The dual core opteron models start at 1.8 Ghz with the 165 and Go up .2 Ghz for every model you go up. (ex: 1.8 2.0 2.2 2.4 2.6)The models are: 165, 170, 175, 180, and 185.
I own an opteron dual core, a 175. The only diffrence between an atholon and an opteron is Overclockablility. My Optetron 175 went from 2.2 GHz to 2.8 and 2.9 with some extra voltage.
How much are you looking to spend?
If you just interested in the switch from the winchester core to the venus then no it's not worth it unless you may overclock, but by looking at your ram, I don't think your going to.
May the wind always be at your back and the sun upon your face, and may the winds of destiny carry you aloft to dance with the stars