Hey Y'all, thought I'd post a little knowledge for anyone else putting their own audio in a NBS (GMT900) series pickup. I personally have an extended cab Silverado, no On-star, Non-Bose LT-II. I installed Infinity 6.5" speakers in the rear doors using the stock wires (they fit right in with the provided bracket). I also kept the O.E. head unit. Everything else changed. I wanted to amp the front speakers and a sub. I custom built a box to go under the passenger side rear bench, using a Kicker 10" (Comp10). The amp for all of this was an Alpine 400w 4 Channel. Everything else installed pretty easy, but I made the mistake of putting the amp on the transmission hump in an attempt to save some storage under the driver side rear bench. The amp gets too hot that close to the seat and will shut itself off, so I had to mount it under the bench on the driver side. The front 4 speakers I replaced with a set by Pioneer, that came with signal splitters, which I installed under the dash and ran new wires to everything up front. The tweeters were a little hard to replace. I cut the post trim out wide enough to hold the new speakers and used krazy glue to make sure they didn't rattle away. The doors were 6.5" and also fit in with the provided bracket. It almost looked like a 6x8 would fit in there if you were feeling frisky, but I didn't want to try. Off the head unit I used a 4 channel line out converter and spliced it into the existing harness. F-L is CH1, F-R is CH2, R-L is CH3 and R-R became CH-4, then I used channels 1 and 2 for my front sets and bridged 3 and 4 for my sub. My opinion, the hardest part was getting new wires into the door panels through the existing grommets. My goal was a cleaner, fuller sound without taking away the factory look. I also have the added bonus of having enough bass in there (by upping the amp) to rattle things apart if I wanted. That Alpine has more than enough power for everything, it just tends to get a little hot.