I personally can find nothing wrong with the standard system compared with the upgraded on the T5 or the T6.
It is a glass and metal box that can travel at 130kph , with passengers sat next to one or more speakers rather than in the centre of the sound stage.
Next, the music files played nowadays are computer generated digital sound files that lose quality on conversion and then often received at the head unit via a FM or Digital Broadcasting system.
It is extremely rare to have a Symphony Orchestra playing at Wembley Stadium or Black Sabbath playing at the Albert Hall.
So, if you have a wide ranging love of music then listening in a 5x2x2m box trundling along modern roads at high speed just isn't going to do it.
I think if you want that quality on the move then a system that uses high definition headphones to the listener as the final pathway is the best way forward.
Or just have a good system at home and go to live concerts .
Audio in a Campervan has to be a compromise, and don't forget high decibels when young means low decibels when older.
Anyway, the system switches OFF after 20 minutes when parked up, so probably better to spend on a good system to use when camping.
Just my personal thoughts.