Anyone have any experience in car audio?

Dynamat can be an expensive venture. Especially if you do it right. But if you do decide to do it, do it right and spend the dough. One square foot pieces here and there won't do a thing to help you. Its all about full coverage. You'll need to pull the floor liner and spare tire, the trunk liner, do the wheel wells in the trunk, if you can get to them - the wheel wells under the back seat, the floor, pull the headliner and cover that, the firewall and line the under side of the dash under the steering column, all the doors, the speaker wells against the door sheetmetal and two pieces over eachother under both license plates. You're talking close to 100sq ft. That's close to $250 not including labor if you have someone else do it. And that is doing it right. And your car will be a little quieter but the sound will be much better.

It's about getting the acoustics inside correct. You won't quiet the outside world regardless of what anyone says. Dynamat doesn't do that well. It is designed to keep your panels from vibrating and resonating in order to get the sound better inside. But you will see great results if you do it right.

And your car will be 75lbs heavier. ;-)

I Put way too much money in mine (Focal utopia components and 11" utopia subs run in stereo with a Esoteric Audio E7402 and Zapco Competition gear.
All I have to say on this one Is its all about amplifier quality and signal gain, Do you have an Equalizer/Crossover?
The audio control DQ components are great and only about $500,
That will Give you a good amount of signal boost to your Amplifier and will probably give that boost your searching for without using equalization. However I would recommend a subsonic filter set to 20-25 HZ as only your neighbors will be able to hear that wave and it will ease the job on your amplifier significantly
Also I am not sure of your budget or your subs but the older Zapco competition amps are way down in price well below $500, My Z350-C2sl I think is the name, something close pushes right about 350 watts a channel and does a phenomenal just phenomenal job on my 6.5" Midrange's
Those amps are great and ignore the rating i think my amp is rated at 30 watts x 4 but pushes about 85-90 RMS and bridged is pushing well over 300

Oh to the best of my knowledge you dont damage your hearing from low frequencies its the higher pitched frequencies that destroy your hearing, Please shoot back if im wrong id like to know.

High pitched frequencies can certainly hurt your hearing, perhaps at lower SPL than lower frequencies but SPL is SPL. They'll both do a number on your hearing.

And I love the guys that walk into audio shops and demand the biggest speakers that will do 20Hz. Dumb.