Car audio is pretty complicated. Licensing home audio companies to put their names on car audio systems is kind of a joke. I am sure the companies try to do whatever they can to help out, but no one gets into their car to listen critically to music. If the do, they will be disappointed.
A graphic equalizer may help some, but cars are for driving, and listening to some tunes is nice, but it ain't home audio and never will be. As for companies like Bose (PLEASE!) and Mark Levinson--oh, my--well, you wanna pay extra for those names on you speaker grills, go buy the little plastic name things and paste them on, I guess.
Cheers!