Many, many years ago when I was going to install carpet i covered the firewall, tranny tunnel and floor with an insulation that I got from, I think, JC Whitney. Before insulation my feet boiled on a hot day. After insulation hot feet became a non-issue. I have a 1A with vents. Definitely something that is recommended.
If something is listed as thermo-acoustic it seems like it would serve 2 purposes, but I would want that fact comfirmed.
Mark L