2002 explorer bass wiring

I've searched here, and found a wiring list for a 2002 Explorer, but it only includes the main speakers (wire color), but nothing for the bass or amp. Below is the list I found: |        RADIO 12V|lt GREEN/ purple     |+ |at radio     | |     RADIO GROUND|black|- |at radio     | |     RADIO SWITCH|yellow/black        |+ |at radio     | | RADIO ILLUMINATE|RED / black           |+ |at radio     | |       LF SPEAKER|org/lt grn-lt blu/wh|   |at radio     | |       RF SPEAKER|wht/lt grn - grn/org|   |at radio     | |       LR SPEAKER|tan/yel - gry/lt blu|   |at radio     | |       RR SPEAKER|org/red - brn/pnk   |   |at radio     | What I would like to do, rather then tear apart the rear passenger cargo area, is splice into the line somewhere before the amp and base.

If you are only wanting to integrate the sub bass then metra sells an integration harness for the premium system that has an rca that you can use to plug in to whatever you are using.Gary Sather