2005 Chevy Tahoe Stereo Info needed

A buddy of mine just bought a 2005 Chevrolet Tahoe, and wants to get rid of the bose speakers(They really aren't very impressive)  Anyways, does anyone happen to know what kind of setup it is.  I understand it has 6.5" components in the front and rear doors and a 6" sub in the center console.  Does anyone have some info on the amp set up?  Can we just swap the speakers and run off the stock amp?  He's not oppossed to picking up an amp, but doesn't want to swap the head unit.  Thought about suggesting a 5 channel amp with speaker level inputs if we do need an aftermarket amp to push the speakers. 

He's not looking to do anything too fancy and wants to keep a factory look because he picks up clients for lunch all the time.  Thanks for the help guys. 

Hey, thanks for the info, I'll be sure to let him know.  They guy at the stereo store was trying to sell him a bunch of stuff I didn't think he really HAD to have. 

Do you have any pics of your Camaro setup?  I've got a '98 Trans-Am WS.6 and I'm trying to formulate some stereo ideas for it. 

Also, do you happen to know what subs are a direct replacement for the 6 incher in the center console?