Lol, I have been a sound engineer for the last 24 years and if you knew what you have posted you wouldn't have posted it.
If you have ever been to a concert or if you go and look at speakers with that level then you will notice they are
ALWAYS built into wooden boxes. This is because of the effect the box makes to the sound of the speaker, also the inside of the box has a certain shape to reflect sound in the right directions.
With all those speakers in your car....even if they are mounted on wood they will always sound similar to speakers built into a biscuit tin.
Sub speakers move a lot when they make sound...the speaker cone also moves air about, sub speakers can't work properly in a closed box, if you don't have your windows or the doors open they´can't work properly because the air they move doesn't have anywhere to go.
If you knew that 500W of sound at full level(500W) would probably make your ears bleed and that for any car system 100W for each would be more than enough for very loud and (relatively, cos of the tin box) good sound you wouldn't have fallen for the big numbers sales tricks of the car radio sellers.
