I have a 2005 S80 that I just purchased used. I do not believe it has the upgraded sound system. It sounds awful. The sound is shallow, and adjusting the treble, bass, and fader does nothing to clear it up. I want to be immersed in sound, but I can only seem to get my feet wet. Is there anything I am missing, or what is my next move?

I do not have the amp under my seat, and I would love to upgrade. I am considering adding the amp (provided I can find instructions on how to do so), and if necessary, replacing the speakers with JBL products.