I have a 19 2500 Limited with the HK system that is in the shop right now for 3 recalls and one of them is the rear camera which deals with the radio. I Know there is a service bulletin dealing with the HK system, hope it comes back with better base. with that said I had a aftermarket sub and amp in my 2010 Laramie 2500 with the Alpine and since my Limited is the Gen4 interior the custom sub box will fit under the rear right seat were the factory sub is. From the research that I have done the HK system requires an inline module PAC Audio adapter AP4-CH41 revision 2. it hooks inline behind the radio and allows you to use line out from module to amp without using a line out converter using speaker outputs from factor amp. retains all of factory bluetooth, warning and chimes. The pac audio web site will break it down. One other thing that needs to be done is pull out or cut the noise cancelling microphone input wires To the factory amp (there are 4 of them) to prevent a feedback from aftermarket equipment. I have also read that some have replaced the 3 1/2 speakers in the dash and the 6 1/2 door speakers. I am not sure what ohms those speakers are I may just replace the sub and leave it like I did with the Alpine in my 2010. Hope this helps