I know this may be late but I searched all over the web to find an easy answer but I never did find an exact answer. I just recently took my audiophile subwoofer out from under the backseat of my supercab and I thought I could just use the existing wires for my LOC, I was wrong. this is to clear up someone's question like I had. After finding out the sub wire was already a low signal and reading that you could not tap into the speakers for a high output signal I thought I was screwed. I used the existing remote wire from the harness in the back then I spliced the rear speaker wires to attach my PAC LOC. next I ran the RCA wires to the amp and turned it on and it worked with a few tweeks to the converter.

I read time and time again that you could not tap on to the rear speaker wires if you had the audiophile system because the frequencies were all different and all what not but that is incorrect. I keep my stock 6 CD player as well. If there is any questions I'd be happy to answer and upload a video because it was really easy.

A blind squirrel finds an acorn sometimes.

 

I think most people just choose not to because the audiophile deck has a built in crossover to cut bass to the speakers, so I think your missing some low low end. I had mine spliced with a LOC but I sold my audiophile for that reason