DecemberMan24

Hey guys, I was wondering about hooking up a sub and amp to my 06 cobalt ss that already has the 10 inch pioneer and built in amp in it. I have an aftermarket deck with a pac the plugs into my harness, now what I am wondering is can I hook up my other sub and amp and still have the built in amp and sub going at the same time? What would be the best way to put in my aftermarket sub and amp and do I have to disconnect the built in amp to do so? I know I could hook my new sub and amp up but im afraid I have to disconnect my stock sub and amp or I'm not sure how it works. Thanks for any help.