There is a 40-pin WHT connector behind the knee bolster (C200) by the steering column. Since you have the Monsoon system, all four audio outputs are routed through this connector. Here is a reference:

LF (+) Pin C4 - TAN
LF (-) Pin C5 - DK GRN
RF (+) Pin D1 - LT GRN/BLK
RF (-) Pin D2 - LT GRN
LR (+) Pin C8 - BRN/WHT
LR (-) Pin C9 - BRN
RR (+) Pin C7 - DK BLU
RR (-) Pin C6 - BLK

Hope this helps. Because the conductors are twisted, this provides some degree of shielding. It won't be as good as connecting closer to the head unit, but it'* much easier to work on. I'd give it a try and assess the results.