what stock sound system do I have?

Hey all, I bought a 2005 300c used form the dealer with 8k on it and when I bought it it had all the features plus options I wanted on it, including the sound system. Until today I noticed I don't have a center channel speaker, and no rear deck sub. The option lists says the car has the 368watt amplifier. SO do I even have boston acoustics speakers or are they the chrysler brand. And is there any way of upgrading to the ba speakers now? The car has a ton of bass coming from the front doors but very little from the back.