Jim, while I have not personally had mine out of my truck, I have done a bit of research and seen my fair share of factory speakers. My 2015 Silverado NON-Bose is no different than many other cars. Although "paper" is used somewhat loosely, they do resemble a thicker construction paper like your kids would use for arts and crafts. While they don't sound like garbage, the paper speaker doesn't really give the best sound. I have a 2007 Corvette that came with the factory Bose in it. Now that was GARBAGE! I took the Bose speakers out and put in some good aftermarket speakers and it is a million times better. Still use the Bose subwoofers that are in the doors, but it works great for me. I like the sound of the exhaust and headers more than the stereo myself.
Back to the Silverado. The speakers are a paper type material, and upgrading them along with the Kicker kit I am planning to pick up soon, it should all sound much much better. I don't care to do too much custom work on stereos. Plug and play is more for me. Just don't care enough to go all out. I have heard the Bose in these trucks and they do sound better, but I couldn't justify the cost for what you are getting. I also have a bench in the front, so I believe I wouldn't have a sub if I did get that option as it goes inside the center console if you have the bucket seats.
My opinion is to get some nice speakers and adapters and plug them in. Nothing too crazy, but that is just my taste. The Kicker Soundgate kit I am getting will make the speakers sound even better, so it will make the small investment in aftermarket speakers a worthwhile one.