David Paul
Full Access Member
Run your new sub amp off the Pioneer's subwoofer RCA output. You don't want a line converter, that's only for when you don't have a subwoofer output. And yes, run main power for the amp from the battery with a fuse at the battery , ground it well, and your Pioneer has a remote turn-on output wire to turn the amp on. You can leave the rest of your system as is. Your Pioneer has full control of the new subs and amp if you do it this way.
Red is spot on with this. This is how I wired my system but with Alpine components. I'm very happy with the set up.