I am not sure if those were suppose to be links but I used the
Noico 80 mil 36 sqft car Sound deadening mat on my front/middle floor. It seems like a very nice product and pretty heavy. The Sub is still getting body work so no review of the performance. I used the Eastwood version on the floors of my '72 Corvette but I haven't done any long trips to tell how well it radiates heat away. The fiberglass floors would become unbearably hot in the summer on a long drive.
I haven't used the foam. No idea if it would be effective. Certainly it's not going to work at a radiant barrier.
edit: I used
Reflectix under my headliner in the Sub.