Haha jeez. In HS I had a good friend who had a competition setup in his SUV. 2 15's (i think) in a custom ported box. It would literally make you nauseous if you chilled in the back seat with the windows up.
I agree. Modifying a car's audio system is one of the most pointless things you can do to a car. I have neverbeen in a car who's base didnt bump hard enough, or the volume didnt go high enough to pretty uncomfortable levels. Generally, i find people who tend to do this are some of the biggest tools i have met and are those kids who just blast music in parking lots like a bunch of faggots.
Oh believe me, I agree 110%. Im all for putting a decent audio system in your car (10", 4x6s etc...) My car is where I enjoy my tunes the most. Its not like he would roll around with it cranked all the time, just when he felt like pwning some clown in a rattling civic or when he was in comps.