if you are getting too much of tweeter , set amp at 130-150 hz at HPF for front speakers. and decrease the treble from HU.
i had pioneer HU 1 year back. in that there were SLA 0/1/2. i used to put it on 2 for better sound. And switch on sound retriver as we all use compressed mp3 songs nowadays.
Let the professional do damping. there is a different material used for damping and they know where to put them.
and open the door panel and find out which part is producing noise. maybe you wont need damping
even i need to put damping in the boot of my verna.