Teenagers with hot rods.
Helpful hint: if you're going to have the stereo system, you must first make sure that your car is:
1) painted (primer and bondo do not count, unless your in that auto club)
2) Has no donuts for tires.
3) The vehicle not given to you by your grandma (unless its really a hot rod)
4) engine and undercarriage in working condition (if you have a blown head, why would waste money on the stereo before fixing that?).
And most importantly...
5) go out and buy that $5 tube of caulk so that you can insulate your vehicle so it doesn't shake apart (a good car should only ever purr or rumble, never rattle or clank).