I got a great response which clarified a lot of things for me... have a look... It still doesn't solve the wiring harness issue but so far as the Monsoon is concerned, it's a nice explanation...

<snip>
Hi Jacob and David,

The Monsoon system amplifiers use current sensing to turn on (wake up),
instead of using a separate remote turn-on lead.

The amplifier uses the DC offset that is present on an amplified, speaker
level signal to wake-up. An RCA-type signal does not have this offset, which
in turn does not wakeup the factory amplifier.

It seems that all eight speaker leads need to be hooked up before the
amplifier will turn on. Also, the Monsoon amps do not like the MOSFET-type
outputs that are present on most new aftermarket radios. It looks like the
stock VW radio is about 12 watts per channel, so we usually recommend that
people stay with lower-power-rated radios (or amplifier in your case) when
doing this integration.

Your best bet, Jacob, is as Dave suggested.. just buy a nice little 20watt,
4-channel amp and use it to integrate into your Monsoon amp.

Hope this helps,
Rob Putman
SoundGate
<end snip>