Audi: 2000 Audi A4 - Upgrade rear amplifier and speakers

I have a 2000 Audi A4 with stock head unit and speaker/amplifiers. In
the trunk, the wiring harness plugs into an amplifier which is located
under the left rear speaker. I would like to keep my existing head
unit and wiring harness and add the following upgrades (Eliminating
the stock rear speakers and amp):

-- Carver KMOS 2150 2-Channel Amplifier
-- Boston Acoustics 6.5 components speakers to the rear deck.

I plan on running 12V+ with a fuse block right from the battery
and ground the amplifier to the frame. Is there an aftermarket wiring
harness kit available anywhere that will allow me to plug into the
stock wiring harness (in the trunk), in effect giving me the available
line-level left-right signal and remote power feed needed to run my
amp (without cutting the stock wires)?

Okay, if I have to cut the wires I will. So I guess my other
question is, has anyone out there done a setup similar to this before?
And if so, could you tell me what each colored wire is for?

Thanks, Hertz

http://vader.inow.com/~drbob/carstereo.html

this might help you...