There is a place that sells custom subwoofers box that fits right under the first aid kit. It matches the same trim and you cannot tell that you have altered it. They are 2-8" subwoofers.
They will send me some brochure and we'll go from there.
These are designed to give that extra clean bass but not really sound like a big boom box per say. I do need the space in the trunk as I have kids, soccer, basketball.
Regards
Barry-1990 300CE