My prediction of temperature increase for in case was wrong for the Zalman heatsink; comparing to the bench test, it ended up close to 30 degree Celsius increase. The heatsink had been reset couple of times to ensure correct seating, but the results were the same:
The temperature of around 80 degree Celsius at full load is too high and maybe kbrady1979 was right, "You get what you pay for most of the time."
The Zalman CNPS9500 AT 2 was replaced by Noctua NH-D14 and rerun the turture test by Prime95. The open case test looked good:
After closing the case, the results didn't change much:
That's pretty good temperature for full load with the case closed. At idle temperature of the CPU is also pretty good:
What can I say, you were right kbrady1979...
* The case is an Antec P183 with four 120mm case fans for both heatsinks. The ambient temperature was around 20-22 degree Celsius during both tests.