I dont know about your system specifically, but I went with the alpine pxe850s digital signal processor/12 channel amp combo. The factory wiring plugged right into it (speaker wires from truck), then I added the 4 channel amp for the doors and sub amp and 2 12" subs. The dsp controls everything and the stock 8.4 with nav handles the selections of music etc.
Took me a while to figure out how to make my phone notifications not try and blow my ears off when on bluetooth lol. Had to turn the level down on blue tooth on the dsp.
Anyways see if crutchfield has anything available and research from there. It also will matter if you have the harmon kardon system or not.
Edit: keep in mind you dont need a 4 channel. The 25 watts the alpine puts out works very well. It's running my dash center and ceiling speakers and they keep up with the doors and arent over powered by the subs that get 1000 watts
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