Add Kicker subwoofer and amp

[Grumpy Tooch]

I have a 2016 GMC Sierra 2500 SLT with BOSE system.  I am looking to add a subwoofer and amp to the already existing system without disturbing it.  I only want to ADD the subwoofer, not replace any of the existing system.  I've found bunch sub enclosures (ebay) and kits that come with amp and wiring.  This I've dine many times before but what I am not certain of, is what connector I would need for the stock head unit to allow me to connect another amp.. Or, are the provisions there already?  I haven't opened up anything just yet.  If anyone has done this or is planning and knows what i would need, greatly appreciated.  I also would appreciate any links to other enclosures and equipment that would fit my rig.  I know GM makes one for the newer trucks but i haven't been able to find one for my year.