You have the monsoon system most likely if it says monsoon. The amp would be behind the back seat in the trunk, under the plastic pannel. also look on the bottom of the speakers in the trunk they will tell you bose/monsoon. I dont know about the monsoon system but the Bose is hard to find speakers for becuase it is a 2ohm system. I rember seeing a few topics on installing an I-pod but they were all jus brainstorming, I dont know if somone actually did it though. There are harness adapters for the 2k cars if you go for an aftermarket HU but I think you will loose things like HUD, alarm, and onstar to name a few, I am sure there is more than those three though. A few of the 2k cars here have opted for infinitys basslink(self contained amp+sub unit) seems like it would be a really easy install, and you get to keep the goodies that youy paid for.
Gutted air box, K&N drop in, MAF screen put back in , NGK tr-55 @ .55, 180* drilled t-stat, INTENSE 3.4mps, Aeroforce, High-flow cat, and one BIG F-ing smile.