Say i lift up the boot and the amps infront of me, on the left handside nearest the wiper motor end on the amplifier theres a wide terminal which houses a blue and black wire and on the right a slim terminal with a slim red and white wire.

In the Haynes it shows 2 wires running to the head unit from the amp. Was thinking, bit strange how the earth would need to run the full length of the car. Was wondering if one wire is permenant live and the other ignition on or something?