What if?
 

What if i wanted to install a new head unit with the amps in the boot of the car and a new sub under the seat plus new speakers ( replacing hiline system) would i need to re wire the whole thing or could i use any of the current wiring? Cheers.

If you wanna run amps from the boot you would obviously need to run a power cable from battery to amps, then new cable for the sub, then I would run new speaker cable from the amp to the front speakers (a high quality one) and then patch into existing wire for rears!