I'm looking to add an amplifier to a non-HK Audio 20 setup ... I'm presuming that the amp goes in the foot-well where the HK one goes but does anyone have a wiring diagram showing where I can tap into the speaker wires together in one place?
The amplifier and component speakers alone made the biggest difference to the point that the sub isn't really necessary, it just adds an extra layer of weight.
The amplifier is compact enough that it fits into the enclosure in the foot-well where the stock amp would be. The subwoofer then fits on top as per the article referenced above. This brings some easy of installation as the speaker out from the head-unit can be split in the one place to use as line-level input to both the amp and sub.
If anybody is thinking of doing the install then just ask me for any details you need.
To answer my own original question, the easiest way to tap the speaker wires was behind the head-unit as it's actually easily accessible - the centre console is only a few bits of plastic to pop-off and a few screws to remove.