@Rowein I have also spoken to BMW genius and they are not precisely aware of the car’s spec although that’s their job to know.
I spoke to BMW Park Lane one of the most popular dealers in London and the salesperson informed me that the i4 edrive40 as standard comes with the 10-speaker HiFi.
In fact if you go on the BMW configurator and select the M Sport Pro Pack there’s images of what comes in the pack but there’s also small writing that lists all the specs on the left side of your screen which shows the e35 DOES come with 10-speaker as part of the Pro pack. It seems to be like this:
i4 M Sport (no packs) – 6-speaker Base
i4 M Sport (Pro pack) – 10-speaker HiFi
i4 M Sport (Tech pack/single option) – 17 speaker HK