I've been testing an XP1600 for the last week or so. It is at all stock clock rates, voltages etc.
At idle it is normally around 38-39C. Running Prime 95 it has gotten up to 49C temporarily, and then settles back to 46C (why?). My system temps seem to stay at 28C steadily. Room temp has always been around 21-22C.
So it looks like I'm seeing around 10 degrees C rise for Prime 95.
If only I could get my system temps down a few degrees, I think I would be seeing lower CPU temps. But now I'm down to doing hard stuff like improving airflow through the case, bah.