Hi Ladic. Most of the xp2500s I've seen , idle in the low 40s. A clean heatsink is important. If you have a vacuum with a blow option, take you computer outside (when it's dry out there) and blow the daylights out of it.
The chips that run hotter than normal, usually have a power supply that has only a single, back mounted fan. For as long as they have been making xps, Amd has stated that the psu must have a bottum fan. This setup usually lowers chip temps by 10c.
Since a psu is always reusable, I recommend that you splurge on a good one. Enermax makes some great units, as does fortron.