For thermal compound, I used Arctic Silver 5, even prepared the surface with Arctic Silver ACN-60ML (2-PC-SET) Thermal material Remover & Surface Purifier. As for being positive that is is seated well, as far as I know it is. Brackets, backplate, and cooler were all cranked down good, and used a grain of rice sized bead of Arctic Silver 5. The fans on my antec 900 are set up just as they come...all medium speed, the two 120's in front are bringing fresh air in, one 120 on the back exhausting, the 200mm on top pushing hot rising air up and out of the case. The one thing I have been thinking about is that the rear exhaust fan is right behind the monsoon. Could the monsoon be getting slowed down by trying to blow through the exhaust fan, even though they are both blowing in the same direction? Maybe I'll pull it off and see if the monsoon cools more efficiently.