Reading Topic: Aftermarket stereo installation and pictures
I have two whole rolls of film I need to develop detailing my 2000+ W sound system install. I'm waiting for the weekend too, so I can get my film developed, and website updated. Also I've got the wiring color codes for the door speakers, I will post that on there as well.
I'm with you on the preamps, I wanted to tap in there too. There is a single harness going into the back of the radio, I'm assuming part of the harness is the pre-amp output to the OEM amp. The problem is, it's really awkward trying to hold the entire center piece, turn on the radio, and then somehow attach an external speaker to each jack until you find the pre-amp. Usually to do this, I take the speaker out of a pair of headphones, solder a stick pin to each lead, then push the stick pins right through the insulation. Once I have one stick pin set. I touch each of the other wires until I hear it play. Mark the combination of wires that makes the speaker play, then on to the next pair.
The trick is to use a very small speaker, pre-amp outputs are less than 600mA. Also, the other trick is to keep from scratching the center piece

The big metal gearshift in the middle got way too close for comfort a few times.
If you get the pre-amp color codes figured out, def share, I'll pull my HU back out and tap in if I get the codes.