This topic is of interest to me, as I have invested perhaps more in audio systems than I have in the actual cars themselves. Each of my cars has a McIntosh 50x4 amplifier, MB Quart speakers, a separate bass woofer and amp (Kicker) and a BBE unit. The last item I think is most crucial in developing clear treble in the front, even with MB Quarts. There are three head units: a Philips DC532, a Becker Monza, and a Sony 620 (Jacky's in Dubai was the source here) with short wave.

Of necessity the front speakers are 4", since the smallest speakers with separate tweeters come only in 4" size with MB Quarts. The tweeter cones are separate. My installer mounted them on top of the facia. The back end of the fascia is raised slightly. No problem. I think the sound dispersion improves.

I also have installed the Sony XM tuner in all three cars. That programming is a joy to listen to, as I have a full schedule of classical music, old time radio, plus the BBC World Service, at my finger tips in clear sound, no matter where I am driving, be it on interstate highways or on country roads here in the rural mountains of southern West Virginia.