Great upgrade? Nope. Worth $80? Probably not, unless you make money by encoding video. You may get an extra frame in games where you are already 100+fps. If you dont have a matched pair of decent ram, expect to see a slight loss in perf, untill you OC.
I wouldn't recommend any OC without some serious after market cooling.
If I were you, I would sell it and build an A64 system.
Prescott is a bad design.