How much sound insulation?

[sbrban]

you guys are missing the important area...the firewall. You will get a LOT of noise and heat transfer from the firewall alone.
I used ice and water mat on the firewall and floor of my burb. Ive used it in numerous vehicles with good success. I heat it up and roll or press it into the floor pan areas. you don't need to do the entire panel, although i would say I probably cover 3/4 of each panel.
After that I'll put down a jute backing and on top of that would be the carpet. The jute backing I do put across the entire panel if it's possible.on the roofs, I'll apply the ice barrier in sheets about 12" wide going across the roof from left to right.After that a roll of jute that is sprayed with adhesive spray. I can't say if it has fallen down-I haven't had a reason to take the headliner down to see.