My 5 has the front mid range/tweeter combo and two speakers in the rear. I have the basic Sport model so I doubt I have premium sound. I was looking at doing custom 8" subwoofer pods where the rear speakers are located. I wanted to keep the rear fill by placing them somewhere else and was also wondering if there were speakers in the sliding doors or somewhere else on a higher model.
Oh.... well I have a 2006 Touring manual trans with OEM navigation (basically the top of the line model for 2006) and mine only has those same 6 speakers. Mine does have the 6CD changer if it makes a difference.