At the end of the market where Jack, I and I suppose most others on this forum buy their cars, wind noise, road noise and engine noise (plus rattles, friends, alternator belt squeals etc) will cancel out the good points of ANY expensive sound system.
Sure you can 'optimise' it for when the car is stationary, but because the acoustics of cars are pretty poor anyway that optimising isn't going to be as far reaching as it could in a solid structure - a building for example.
But you can't optimise it for all conditions. What might sound good (and I don't speak about volume - most songs and tunes are ruined (imo) by excessive volume, and cinemas pander to the idiots by turning up everything - WHY!?) with just you in the car on a silent summers day will be utterly ruined at 60mph with 3 mates in the car on a rainy winter's morning...
So why spend money on a sound system in that type of car? I'm sure it's a bit more worthwhile in a decent car - even some of the more expensive Lexus, BMW, Mercedes etc will have a solid enough structure and reasonably suitable acoustic properties to get an 'okay' sound, but it will still be cancelled out by beating rain or tyre roar.
Each to their own. If you want to waste money on a sound system you'll never be able to take advantage of then that's your call. I waste my money on a racing car that doesn't really go much faster than most road cars, and plenty here would rather not.
And the chav thing was a poke at sam38 with his £200 van with an £8000 speaker in it.