I have a 2012 ram 1500 big horn quad cab with the dual exhaust coming out the back. I want to leave the stock exhaust coming out the back but I want to change the muffler to sound better (louder). I am going to go with Magnaflow since thats what I had on my old truck and the sound was great. I'm trying to decide between an 18" or 14" muffler. I don't know if the 14" will be too loud in the cab of the truck or not. Any suggestions? Also does anyone know if changing the muffler will affect the factory warranty at all??? Thanks for the help!!