Thanks for the detailed post. I'm sure those that worry/obsess about heat will find it useful.
I don't think the RT-N66U runs hot. At least mine doesn't. I've used a temp gun. It's not even warm to the touch except near the power button. I use the little plastic stand thing that came in the box. It sits in a room that is 65-70 degrees F. year round with good air circulation.
I have a Linksys EA4500 that runs very warm to touch on bottom as it sits flat and temp gun confirms. It has worked fine for 1.5 years.