Aftermarket sub and amp in a A3 SB

[grimp]

Hello!
I have decided i want some more bass in my car, im thinking of buying this:
http://www.amazon.co.uk/``Alpine-SBE-12KIT-12````-Subwoofer-Amplifier/dp/B002SALQV2

i have a RNS-E 193 G head unit without Bose, question is, what do i have to do to get this working? After what i have understood the rear amp gives power to both the subwoofer and the rear speakers, is there a way to keep the OEM amp for the rear speakers? and use the aftermarket one for only the subwoofer? Can i get the signals/remote from the rear(OEM amp) or do i have to pull wires all the way from the HU? If i can use the signals from the rear amp, which ones do i connect to the aftermarket amp?

ps. the aftermarket amp does have high input

your wisdom will be very much appreciated

 

[dualmono21]

yes it can be done
but if i may offer a suggestion
use the standard amplifier to power the FRONT speakers buy running new wires to the front speakers
then use the new alpine amplifier and sub to power the rest of the system

the only other thing you would need is an iso adaptor which lets you output to the alpine amplifier
(i wouldn't recommend doing it by high level input as you will pick noise up through it )