I can assure you that a watercooled P4 2GHz on an ASUS board with plenty of fans and massive airflow, including the mentioned 450W PSU runs in idle at around 58 degrees, also under extremely heavy load never ever went above 68....
At around 89 degrees you approaching the temp which the tiny little bits and pieces inside the CPU destroy....
Everything above 80 degrees should be considered as dangerous and you should re-consider the cabinet and/or devices providing a better airflow...