premium sound package

Hey all, anyone out there got the premium sound package on their Montana? I was wondering if that means you have more than the 4 speakers in the stock montana? I think i've got every option, except for premium sound package, and so only 4 speakers. This really makes it hard to hear the stereo on the highway without blasting the rear passengers out. I'm wondering if I could "convert" my van to the premium package by adding speakers (hopefully the extras are in the dash, to complement the weak dork panel speakers that are mounted too low to hear well). Anyone know if they have more than 4 speakers in theirs? i'd be interested to know where they are located.