If you already tried to lower the volume levels based on section M, but the low music quality remained, then you have an other problem. The Stream, Stream MP3 and Dance radios from Skoda were manufactured in more factories, some of them were made based on the Skoda specifications, some of them were made based on the Volkswagen specifications. The difference is on the CD changer connector, where you install/connect the Gateway device, the pin outs are different in case of the Skoda and Volkswagen specifications, basically two cables/pins are replaced with each other, that causes that the Gateway is recognised and working, but the sound of the music is not full. There are no low frequencies, or other frequencies can be missing too, rare cases also noise can be there when music is played. The two replaced pins are indicated with red and green on this photo:
This means that the Stream and Stream MP3 radios in 90% of the cases might have the Skoda pin out on the CD changer connector, therefore they work with the Gateway package that includes the CABL-SK1 cable, but in the other 10% they were made with the Volkwagen pin out, so the Gateway package with the CABL-VW1 cable works there.
Though in case of the Dance radio the Volkswagen pin out is more common in 90% of the cases it works with the Gateway package including the CABL-VW1 cable. In the other 10% the Dance radio might have the Skoda pin out, so the CABL-SK1 cable is needed.