I have a 2013 GMC Sierra 1500 SLT that I just bought and I am looking to hookup an after market subwoofer and amp but I like the stock dash look so I don't want to replace the stock radio (which would make this process a lot easier). Would I just replace the stock sub and amp and splice into the current wires? Could I keep the stock sub and amp also while connecting new sub and amp? Does the stock radio have RCA connectors in the back that I can connect too? In a perfect world I would be able to add a new sub and amp without replacing the stock sub and amp and still have a high quality sound system without using RCA plugs since I do not think they come on the back of the stock radio.