That all makes perfect sense to me and it is also worth remembering that car stereos are one of the worst things to listen to anything on, primarily on account of there crap dynamic range. This in conjunction with lots of engine noise, masking anything even vaguely resembling a nuance is basically an audiophile nightmare.

There is a reason why good sound kit is manufactures with low self noise !

Acoustic properties of the interior of a car, well...dreadfull !