The sound quality in our 2016 Cascada is very good. I do not know what kind of music you like, but for jazz, standards, and even most pop/rock it sounds really good. I would compare it quite favorably to the Bose system in my 2017 Corvette Grand Sport 2 LT. I do not listen at extremely high volumes, although we certainly will turn it up loud enough to hear clearly when the top is down.
Perhaps a silly question, but have you double-checked all of your audio settings?