[TuffLittleUnit]

I had a similar experience with an Audi A5. I spent a fortune on the Bang & Olufsen stereo and was deeply unhappy with it but the dealership constantly told me there was no problem. I was sure the volume was limited in some way because if I kept turning the volume knob up the audio volume didn't increase but I had to turn the knob a proportional amount down again before the volume would decrease.

If that doesn't make sense, imagine the knob was calibrated from 0-15. At 10 the volume would stop increasing but if I had turned it up to 15 then turning it down wouldn't make any difference until I got back to 10 again - like the output was restricted at 10.

Since then I've not bothered with the premium sounds systems - I'm very satisfied with the "BMW Business" speakers which I think are now branded as "BMW Advanced" and are about a third of the cost of the HK upgrade.