I picked up the full sound upgrade kit with sub/amp and the additional amp that is installed behind the rear seat.
definitely a low-end improvement from a stock non-Bose system. it surely has a sweet frequency that seems louder than the others. it sounds like certain bass notes are substantially louder than others. I dunno, maybe others are quieter????
I like the factory fit and the way it has storage compartment built in.
Im not sure I noticed much of a difference in the amp for the existing speakers. still trying to tune it all with the flextume app.
I did get the bass control knob. buy the knob if you are pondering, its cheap