I am getting ready to start my biggest build yet. Setup is 4 15" xfl's on about 4.5K in my 2000 Chevy K2500 crew cab. Will deadener really make a noticeable difference? I have never used deadener before. If it really is needed, I definately want to use it. I want to do this right the first time! Approximately how much deadener is needed for a crew cab truck? Also, what are the most important areas to use deadener? Thanks in advance!