Your tempatures are in a safe zone, but may I add you do not want to compare a barton core AMD with any other amd besides XP series. (Try to keep it to bartons too really)
I've got a 2500+ barton as well, and when I did use the generic hs&f it ran temps near the ones your reporting.
But for overall safety and general coolness for your room, I'd suggest getting even a 30$ hs&f.
http://www.newegg.com/app/ViewProduc...=BROWSE&depa=1
Thats what I use, and it gives me idle temps of 35C~ and high 40's for underload. Mind you my system is also overclocked to 2.1Ghz and 211FSB.