Yea there is already an aftermarket deck installed with pre-amp outs but the fatcory amp does not use regular RCA inputs. it has its own proprietary plug (DIN). I found that they do sell an adapter kit that has the DIN plug that splits off to RCAs and the remote turn on wire to turn the amp on when the stereo turns on... which I magically had the adapter already and didn't know it (accidentally bought it a while back and kept it) however some artard cut the DIN cable at the deck plug so now I have to find that cable...

1998 Mitsubishi Montero
2" Body lift
35" Cooper tires
Parrot Asteroid Smart w/ factory AMP
Cobra 29 LX CB Radio w/ Firestik MK-DM18R rooftop mount
Aisin Manual hubs
Grote 36 LED, TractorPlus (Wired to factory fog light switch)