I would do some more homework before you spend a bunch of money on something like dynapad. Keep in mind that anything with a large thermal mass is not an insulator over a long period of time. Something with a high thermal mass will absorb the heat and store it. Then it radiates it back out.
This means that it may work like an insulator for a period of time, then it becomes a heat source once it stores up all the energy. Heat insulation works by isolating the heat source from what you are trying to protect. Look at a double pane window. It isolates the heat / cold by using a layered approach with air as an insulator.
Sound Insulation is similar. It is often made up of layered materials of different densities so that the sound is reflected back when it hits a material of a higher density.
All of this is hard to to in a car where the floor surface is load bearing and materials that are not very dense crush.
