dynamat

Has anyone felt the need to add Dynamat to the doors and/or trunk? I have heard multiple comments about the stereo and it seems that a sub may be the only thing needed though that is user dependent. If I put in a sub I have thought about Dynamat for the trunk and maybe doors but wonder if that...

I saw several videos in youtube about how they make the car quieter by using dynamat? I wonder to know any one tried that on genny and is there a real difference noticeable?