My first car had an AM radio, with one speaker.
We've certainly come a long ways since then.
I thought the radio in my SX4 sounded pretty darn good, when I set the bass at about 80% and then sent 75% of the sound to the rear speakers.
I've done the same thing on my Kia Soul and it too sounds pretty darn GOOD!
I seldom even listen to the radio, because I'd rather listen to my car and what's going on around me, like the ambulance coming up behind me.
These people with their whole car going "BOOM! BOOM! BOOM!" have no clue if they have a rod knocking, tire going Flop, Flop, Flop or if there's an emergency vehicle behind them, needing them to pull over.
I usually only listen to music when I'm stopped, like for a train.