One note about the Scosche adapter cables:

If you want to use the X100M's crossover and subwoofer outs, you will need to bypass the adapter and run your own wires from the front and sub outs to the amplifier.

The stock head unit is two channel. A Y-connector splits the full range signal across both the door and subwoofer channels of the amplifier. That's why the doors rattle so much with deep bass (< 110 Hz).