Hey don't get me wrong. My list was simply ordered by easiest to hardest in terms of solutions to bringing temperatures down.While this has been shown to be effective, I consider it ridiculous that one of the main ports the equipment was designed to use causes the machine to run on the warm side.
The best mod for cool operation is a fan - if airflow can be directed to enhance natural convection currents, pushing heat up through the exit ports at the top from below, so much the better
If you were to ask me the order of the same solutions that was technically "most correct", it would be as follows:
a) Contact Asus and RMA the router (ie. get Asus to fix their mistake)
b) Open the router and modify the heatsink to make proper physical contact with the CPU (ie. fix the root cause of the problem)
c) make sure it is not sitting on top of any sources of heat (might just be getting cooked)
d) Make sure it has good airflow (again, good practice)
e) Ensure your router is clean and free of debris (likely not the cause if passively cooled, but worth checking)
f) Install a cooling fan on the back of the router (can be noisy, consumes a USB port, and attracts more dirt and dust, but can fix temperatures if well monitored)
g) Turn on EEE (energy efficient Ethernet) from the command line, and add it as a startup command. (minor improvement to heat that can be made easily, but does affect performance to a small degree too)
h) Use fewer LAN ports (again, slightly better heat management, but limits the capabilities of the router that you paid for)
The other measure that I forgot, which I would put at the bottom of both lists would be:
i) Turn off plugins and features that cause high CPU utilisation.
This is another measure that should be considered a last resort, since you are really limiting yourself on what these great routers can do.