Thanks Finalazy dude,
I think eventhough we are only installing front speakers, but I guess we should install at other area too to some extend as to dampen those vehicle structure too as to keep the sound of music inside the vehicle while absorbing excessive sound generated rather than keep hitting metallic structure around which create echoes, and also to prevent outside noise from coming into the vehicle which will create noise and also to reduce/eliminate rattle from mechanical movement euther intended or not intended.
By the way, you are right also if we questioning whether the impact (I means installing at other structure) is worth the effort and cost,. This need further experimentation.
With all due respect, again I know what is the cost the material, what I am asking the cost for us to pay the installer (labor charges) to install those material ?