I was trying to add an amplifier and a sub, using the rear speaker wires, however I have run into a bit of an issue, I was following the guide on the front page, but under the CD changer there is no amplifier, in fact on the outside of that plate is a long silver box whch is the bluetooth box.

Can anyone help me locate which wires I need to use for the high level output?

I am in UK, the car an X5 2005 (facelift), it has 16:9 screen, 3 speaker front, no dsp, bluetooth and navigation.

Really struggling, been taking more and more panels of the back but no joy. Is the UK wiring and locations different to US?