Blindside,
I have basically the same configuration that you do. I have a TB 900 and an Abit KT7-RAID. My idle temps are normally 3-5 degrees Celsius about my case temp. After playing Quake3 or Half-life, etc. my maximum temp gets into the low 50s. I have not had any stability problems though. I am using an AMD fan that came with the processor, however, I did buy a Global-WIN FOP32 because they were rated really well. Honestly, the Global-WIN didn't do any better job cooling than the original fan. So, I went back to the original. I am using thermal paste by the way... Personally I think that Athlons just run hotter than most other processors, but I don't think that a fluctuation in temperature is really anything to be worried about. As long as your temp isn't getting any hotter than it is now, I wouldn't give it too much thought. However, if you want to reduce your maximum temp, I would try concentrating on getting the case temp down as low as possible. You might consider adding extra fans, especially if you have a large case. If you find any miracle solution that greatly reduces your temp, let me know!