This "Black Box" you mentioned, is the AMP. I don't know whether it's your OEM ar an addiotional one. But I can show you a pic where it located is and what's behind our back seats. In this pic you can see the OEM Bose Amp
-Mike
Behind The Rear Seat
OEM Bose Amp
Here a pic, how's the OEM Bose Amp look like. If you're unsure, check of its sticker on the back side of your Amp.
Behind The Rear Seat

OEM Bose Amp
Here a pic, how's the OEM Bose Amp look like. If you're unsure, check of its sticker on the back side of your Amp.

