Since you've mentioned noise and Tony mentioned 1700XP and TBirds earlier - the 1700XP puts out a lot less heat than the 1333TBird.
I think it was Tom's hardware that had a big list of power dissipation figures for AMD chips, it is worth checking out if you can find it. Obviously the less heat the CPU throws out, the easier it is to get efficient and quiet cooling. It is easy to save $15 on the CPU only to then spend an extra $30 cooling it.