Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
overpower the sub? I don't get it, when its peak power is at 1000wrms and the amps max is 500wrms?
by the way would the JL 6" splits and the Rockford Fosgate 6" be 4 or 2ohm? or both?
As bezz has said, PMPO/peak means nothing. You can't have a 1000wrms peak sub, it's either wRMS or peak. I'm sure you've already picked up on this, just figured I'd post it in greater detail. Very lucky to pick up a car with JB/rockford gear already installed too.
Good luck with the install.