They run along the top of the passenger side door pillar and back above the
window frame (inside the air vent channel).  Difficult to add another wire
unless you take down the channel.  I ran four wires under the van and came
up into the rear heater area following the hoses into the rear seat area.
I mounted a four wire speaker "pinch" type connector to the top of the
heater cover, which is under the seat.  Now I have two Sony bookshelf
speakers I can put anywhere.   I will have to come up with some sort of
mounting bracket.  They can be stored under the rear seat when not in use
and to keep them out of sight.

                                                             Jay