Anyone fitted one?

At the moment i have removed the bose sub and used a line level converter to plug into my amp.

works ok.

however i would like to get a pre amp signal before the bose amp.

where is the bose amp on a d3 2004 A8? left side in trunk? yes but which unit is it?

is the unit receiving an optical signal from the MMI unit? or can i tap into the sub signal pre amplifier? ie is it a normal copper cable.

If it is optical is there any unit i can use pre amp to let me adjust/tap into the optical feed.

the reason i am asking is taht i dont think i am getting a clean signal and the low bass frequencies are really being cut off and very noticable with 2600rms

here is the box and yes my camera skills suck