As part of the Alfa refurb, I need to replace the factory sound deadening on the Spider. Current sound deadening (from factory?) is a layer of butyl-like stuff that is very brittle, a layer of more traditional foil backed butyl deadening (aftermarket?) and several layers of carpet padding.

Looking on Amazon, it appears I have my choice from 30 mil to 300 mil, costing anywhere from $1.2/sqft to $4/sqft.

I’ve also got choices in open cell vs closed and a everything in between.

My goal is to not waste money so... thoughts?