You'd be lucky to have the 13 speaker system and not just the standard 8 speakers first... I thought I had the 13+ speaker system but truth be told only have the standard 8's... However, I only listen to music from my phone 95% of the time and it sounds pretty darn good. But try to listen via any other source, CD's, Radio, Satellite, etc and it pretty much sux a fatty.
Take a flash light and look into the door speaker grills. You can see if there is a speaker inside them or not. If the door only have 2 speakers instead of 3 each... You have the 8 speaker system.