BMW X5 Urgent help needed to find Audio Amplifier

[GVC]

HI,
I am from South Africa and I have a 2005 X5 3l diesel, I want to fit a amp and sub to my vehicle sound system, but I cannot seem to find the Audio amp to tap off the input as well as the switched 12volt to switch the amp on. Now I know you guys are going to tell me it is at the back on the left behind the fold down panel, but I can assure you it is not there. All that is there is the CD shuttle as well as the blue tooth module. I also opened everything under the spare wheel but there is no amp nor is there a Tuner to be found. I must mention that the sound system is the standard BMW system...
Please if anybody can help it will be appreciated
Regards
Gerhard