I just had my 0550 UPMW Opteron 165 running at 2.65Ghz 1.375V with temps of 65 - 70C at load in a 15" Lian-Li case (2x80mm fans), and an Asus A8N-E.
I got a new case for better air flow (Antec P180 actually), a DFI NF4 Ultra-D, and used AS5, now its running at 50 - 55C (stock HSF, might of applied a bit too much AS5).
Not sure if its the better air flow in the case, the AS5, or the Asus reporting higher temperatures? The Asus was reporting PWM MOSFET temperatures of 110 - 125C (does it adjust to compute the junction temperature???)