[KevinC]

The whole "professional" and "business" naming back then was just goofy, I presume a poor translation from German and not so dopey there.

The Z4 head unit is what it is. What matters is which overall system you have - the standard one or the "HiFi" option with its upgraded speakers & subs, plus "Carver technology" amp (actually made by Lear - who also makes the seats). The Carver system is actually pretty good, despite the lack of features of the head unit.

In 2020 I use my iPhone exclusively for source material, via the aux port. I can stream Sirius XM at 320kbps (thanks to unlimited data), Spotify, my entire music collection, podcasts, whatever. Yeah it's a bit clunky compared to a modern solution, but works quite well and sound quality is fantastic.