Well, I'm running about 500 watts rms daily...
yay for me... //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif
Anyways, they say that sound travels as such...
Every 1 meters, there is a 3dB loss of loudness....
So get metered, and you'll get somewhat of an estimate on how your car will sound, at different distances.
So if I'm hitting 163 dB, that I hit at the comp off of 500 watts, and a 10" Rockford P3, and my car was a perfect vehicle, in which sound waves came out of perfectly, someone on the side walk near my car, playing as loud as it can, will hear sound in the 150 dB range!!!! Crazy!!!
Woo hoo!!!