The Bose dash speakers sound more like a tweeter / midrange hybrid so I left them. Which meant the system was lacking the punch of directional tweeters which I have grown to love in high end car audio systems. They are running off a dedicated Kenwood micro amp in the rear jack space. Aside from subs, the optimal setup would involve having every speaker pointed directly at you.
You bring up an interesting point about music source...it makes such a difference. Songs on the radio are horrible (even HD) and XM/Sirius isn't that much better. Digital versions of songs copied from CD can sound pretty good if you convert them properly/use a losless codec like FLAC (although not sure our systems can play them, haven't tried). CDs obviously sound the best but who listens to those any more!?!
Plus you would need one of those 10 disc changers like they had in the 90s to provide any kind of selection. Pandora, Spotify, etc. probably offer the best mix of selection and sound quality so that is the predominant source in my car. Steaming music is still compressed a great deal which is why I like having the tweeters pull those high hat and snare drum hits out of the song and deliver them directly to my ears.