I just barely received mine, and have yet to hook it up ( waiting for my LCD TV to be installed

).
I talked to an Integra dealer, and according to him it's the nature of the beast, it's due to the amp and how much airflow they have around them.
A unit sitting on an open shelf will run cooler than a unit that is shut in an enclosed cabinet - what I'm planning to do, is to cut slots in the bottom of the shelf that the 806 sits on and install
a small fan on top of mine to assist with air flow through the unit - I'm doing this even though my receiver is sitting on a semi open shelf, I figure that $30 is a small price to pay to ensure that the temps stay under control.
I purchased a aux fan for my PS3 as well, just to make sure that it stays cooler than it would other wise.
I'm probably going to install a USB powered fan in the cabinet it's self so that anytime the TV is turned on I get additional airflow through the cabinet.
If you want, I have spent a fair amount of time, looking at different types of fans and can pass on to you, many of the links I have.