I had the full kicker system installed two weeks ago in my 2016 Silverado and have to say that it really is a vast improvement over the stock system. Overall the sound is more crisp, clear, and "up front" with more powerful bass to complement it like advertised although the rear door speakers don't seem to do much. Like others have mentioned, the door chimes and turn signals are louder but not too bad--I've become accustomed to it now. The sound settings that others have discussed previously matches my experience as well, along with fading to the rear by +1.
One thing that kind of bothers me relates to the void in the mid range that is evident at times. For example, today I was listening to Ozzy's Boneyard and Motley Crue's "Piece of Your Action" happened to be on. The bass, drums, and vocals were great, but the guitar part was noticeably absent at key parts of the song--not even faint, just gone. I'm not sure if this is due to the compression of the music from Sirius XM, the limitations of my stock speakers, or the mix of Kicker's digital processor, but that song was definitely not being delivered to my ears the way it was intended or originally rendered by the artist (It was like Mick Mars took the day off or something).
Those of you who have added aftermarket speakers, do you ever experience this? For almost $1300.00 installed by the dealership, one would think this wouldn't be an issue, but without voiding the warranty on my new truck by doing other audio modifications or installing that $3500.00 Alpine system or something, this seems to be the only option to improving that muffled sound I hated with the original system.
I don't want to sound too critical because I realize the inherent limitations of the head unit and factory speakers, but after making a considerable investment in a new vehicle and the GM authorized "factory fix", I was a little disappointed today. I still think the Kicker Upgrade provides an impressive auditory experience, but it isn't perfect and it is rather pricey.