Thanks for the info.
I used a LOC w/ a pot. from the subwoofer outputs under the center console to install the aftermarket sub amp (RF 30001bd w/ 15" Cerwin Vega Stroker Pro). I also unplugged the factory woofer as this was creating line noise. I still need to run a LOC from the rear speaker outputs for the second aftermarket amp that will be running an additional pair of 6x9's. After adding the subwoofer we realized that this factory bose system cannot provide enough volume to the mid's and high's to keep up with the added bass. At this point I'm wondering if we should have just pulled the bose system entirely and installed all aftermarket components.
I still am not sure which wires to tap into for the high-level rear speaker outputs. I'm going to check the wires at the rear door speakers and see if they match up with those behind the H/U.
2 x DD9515f's, Digital Designs Z1 amplifier