Nissan sentra wiring question

I am putting an aftermarket cd player in my nissan sentra.  It has the Rockford Fosgate stock system in it with a subwoofer and speakers in the pillars.  Is it going to be the same wiring as normal, or am i going to have to do something different for the pillar speakers and sub to work?  thanks!

I just installed the new head unit in my sentra and everything works good except the subwoofer sounds significantly different / weaker than it used to.  I used a vehicle specific harness from crutchfield which included all the wires (for the most part) and soldered all connections.  The amp turn on wire is hooked up (wihout it hooked up none of the speakers work.)  One thing i did notice was that the ground on the new wiring harness did not connect to a pin on the factory harness meaning that it was connected to nothing, and the unit still functioned.  I then grounded the head unit to the chassis and there was no chance.. the subwoofer still isnt as loud as it used to be.  I think the is still pushing it but the input signal must not be as strong.  Does anyone know a way to fix this?  Is there a way for me to turn up the gain on a stock amp?  Thanks in adavance.