Re: sound/vibration matting
Most guys would agree that it does help with 2 things: road noise and bass response. Luckily our Jeeps are pretty quiet as is so to get a noticable performance increase will require you to cover the majority of the door. Not a hard job but does take a little while to get it worked into all the cracks and crevases. I won't recommend a brand as there are many good ones out there with very little difference between them. I personally used the Dynamat SuperLite on my Mustang that had huge interior resonance,and it did a very good job of taming that down without having to cover every square inch of metal.
You can expect to spend about $100 in material for both doors fully covered,so it's up to you to decide if that is a worthwhile investment. You will reduce road noise from coming into the cabin which has the benefit of making the speakers sound better and "bassier". If you plan on spending some good coin on the speakers then i would say go for it.
Another side effect will be a little less "rattle" or vibration of the interior door panel when playing the speakers loudly.
2014 Laredo Altitude. Tinted, SRT Eibachs, Viper replicas.