Power cable to amp in rear trough firewall C5 X7 , any good solutions?

[amigo]

got an C5 x7 2.0 hdi 2009

I want to hear if any do know , if there is any free spots in the firewall i can run a power cable trough the firewall ? I can see on the 3.0 hdi , it do have an extra battery in the trunk, but where is that "original" extra power cable going in from and is there any cable grommet available when i do not have that rear battery installed?

Hope some can help

[amigo]

or how do any route the cable in front to the rear?

[Xantippa]

If it´s automatic, check for the hole for clutch pedal cable in the foot well.

On V6 battery is only in the trunk.

[Sloppysod]

I gave in trying to get a cable through the firewall as it was double thickness, with an air gap didin't try the clutch pedal area.
I know the CanBus system can be very sensitive to current variation, but have you thought of piggy backing off one of the main fuses in the cabin fusebox, the seat heating circuit?

[GiveMeABreak]

To answer your PM, the speaker wiring is not colour specific - in other words they can be any colour.

8435 : right hand rear speaker
8430 : rear left loudspeaker