07 xterra with rf stereo need wire colors

I have a OffRoad 07 Xterra with the Rockford Fosgate Stereo and the Amp is under the Passenger seat, with the sub under the driver seat.

Basically need the know where to connect the Adjustable Line Converter to get RCA preouts for amp to keep it looking stock with added bass.

I added pictures to help, This is the amp spot

https://i101.photobucket.com/albums/m65/xanthan888/DSC02548.jpg

This is the Sub wires going into the box "Im thinking these are the ones i need to tap for going to new amp".

https://i101.photobucket.com/albums/m65/xanthan888/DSC02549.jpg

This is the Adjustable line Converter "LOC" that Im talking about

https://i101.photobucket.com/albums/m65/xanthan888/DSC02550.jpg

Id Appreciate the help.

I understand most people say connect it to rear door speaker wires but im thinking since its the Rockford unit and amp maybe the rear door speakers wont get full range sound from them which would negate the Sub Frequencies i need. ALso im thinking the RF Sub under the driver seat is very low power so it be ok to connect an inline converter for pre out connections.