New Superb company car Amplifier Install

Hello, After a little advice if anyone can help?

Shortly i will be taking delivery of my new company car, Superb Estate SE Business edition, Onyx leather, Metal grey metallic and Laurel wheels and i'm very excited.

I'd like to fit a amplifier and small subwoofer in the boot, I already have an alpine amp with speaker level inputs, so the question is can i run cables from the rear speakers (unsure of location) to the amp of do i have to run from the headunit. 

Many thanks in advance

Odey