Davey, there are two types of music; the one that is recorded to play in your iPod or car, and the other recorded to play in your hi-fi stereo rig @ home.
Like Mike said above; to play sophisticated and detailed classical chamber music, or nuanced jazz music in a car is not the same as in your home system.
Heavy metal, Rap, Punk, AC/DC, CCR, Bob Dylan, ...in the car is more like it, to me. Except that I don't listen to heavy metal, Rap and Punk music, but yes to Bob Dylan and CCR and the occasional AC/DC (very rarely AC/DC...now). I drove a lot in my life because of my work, and I've seen many country sides. I have my own preference for road music. Driving in the city I like Opera. And driving with passengers I like discussions about everything happening in the world, I like to expand my intellect with others, listen to their ideas and drive in life.
Years ago it was different, when in my teens and twenties. With age music habits changed, we adapt/develop newer music habits, it's like automatic for most of us, I think.
There are some music that is so beautiful that no good system is good enough, in my opinion. But we don't think about it, we just gently rock with the music playing flow.
And like Mike said; if you are driving a car that is so silent, so smooth, like a Continental limousine, then Opera and Flamenco and cello and piano and violins and concertos and chamber and jazz and trumpet and acoustic bass and drums and first class Blues and New Age and International/World music is very pleasant.
Folk music like from Dylan, Van Morrison, CSNY, and rock like from CCR, Queen, Led Zeppelin, ...is great for less quiet vehicles, like trucks, convertible sport cars.
That, is my own personal experience and journey. We all have our own and our own music preference for the road, and for home.
To me, depending of the type of vehicle I'm driving, where (country or city), with who is in the car/truck with me; there are some type of music that fits the moving decor better harmoniously.
@ home the decor is not moving, I am much more alert to the simple surroundings,,,six surfaces. Inside a car, through the front and side windows the outside is constantly changing and my eyes have to be alert to those changes and to other drivers too. @ home only the wind, the rain, the tree's branches, the clouds, the birds can move during daytime if you have open window(s). But that decor remains constant and my eyes are not "distracted"; they are smoothly relaxing and not "worry" about other drivers. My ears are fully involved.
Our sound systems sound better when in tune ourselves, when relaxing, when not distracted by our other senses and stressful thoughts or thinking of what we have to do next.
When perfectly in the relaxing mood of the moment, free of everything, we can listen to music with much more appreciation of those better recordings...@ home.
So, your questions and personal preferences are best answered from your own perspective and what your entire aura vibrates best to the music that has that bigger emotional connection/relation with you and you only. We sleep good in our beds, other people might not sleep as good in them, but preferring their own, in their own zone of comfort and independence...own coziness and peace of tranquility.
It's similar with live music concerts; jazz/blues clubs, classical music halls, rock concert stadiums, dancing halls, intimate chamber rooms, etc. And the people too in all those live music venues; sometimes the right audience makes a big difference, other times it's almost like a disaster but we learned from experience to choose our venues more carefully.
Other times we take our chances, we adventure into the unknown...with results that could be ecstatic, musically liberating, or deceiving because of inferior audiences or inferior sound or our own inferior mental disposition. ...Prepared or unprepared, it depends of the reach we aim for.
Yes, keep it simple, go with/in the music moment. And be prepared to switch that dial or flip that record or eject that CD or click on the next selection.