I put my 8" bazooka over to one side under the back seat.  I thought getting it closer to the center of action was better than way in the back.  Like Paul, I'm using it to fill in base.  In fact, I'm not convinced the 8" model is capable of bothering people outside the van.  Since buying it, I've often thought I should have bought the 10" model. In any event, the 8" model does allow the stereo put out good sound while driving, and is even better when stopped.
Tom LaLanne