The round plug is an 8 pin Din plug, that connects the Xanavi to the HU. Supplies the audio from Xanavi, Combo power on trigger, Aux on trigger and the Aux request wire.
The Left hand lower plug is the constant power, ignition on, and the LH/RH speaker wire. I can't remember whether it's front or rear. The right hand plug with 4 wires is the LH/RH speaker wires. Again, I'm not sure whether it's front or rear. The top left plug is the plug that goes off to the stacker. Do you have a patch lead between the main chassis loom and the bottom left plug? You may find that you do and it'll have 2 wires a yellow and red. The is the constant and ignition wire for the stacker.