When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
It’s the big aluminum casing with cooling fins located in the center rear dash/shelf between the two rear speakers.
However, it should be noted that on the Bose system the two front lower door speakers also each have their own small amp right next to them that the non-Bose system front door speakers don’t have.