You do realize we already have a sub right? What you see behind the seat backs are actually bass ports! If we just had a way to raise or lower the volume of the sub we'd be great...otherwise I'm going to try the caps on the front speakers to see if it lowers their function enough to hear the rear bass. By the way anyone interested I found mini 200uF caps at www.partsexpress.com for .09-.40 cents a piece depending on which voltage you get.
Good luck to all on the quest for better sound!

Terry