The box that I was referring to is the one that Dension sends (has you buy) when you select that you have DSP "Factory CD-changer harness connection kit for vehicles with DSP and certain Premium sound system with coaxial connection found in 5, 7, X5, Z4"

It has some RCA jacks and the DSP cable. I ended up not needing it and pluged directly into the CD changer plug.