Take this into consideration as you plan ,, rammat,damplifier, and all the rest of the dampeners are just that..sound dampeners. They are used to dampen vibrations and harmonics caused by vibrating metal. To QUIET(SOUND deadening) the area you must follow on ith another material to actually prevent outside noise from entering the vehicle.
Dampeners add mass to the surface to limit its movement to vibration.Deadeners actually stop external noises from entering.Foam rubber works...lift your carpet up and look at all that matting..thats sound deadener.There are better materials out there though.Bestcourse of action is to Google sound dampers and deadening and read ..some very good articles out there...