I wrote JL customer service directly to get a straight answer on the FIX86 and its placement in the system. Their reply is below. You were absolutely right ctrlz. I guess that's why I haven't pulled the trigger on my upgrade yet, b/c even the high end custom shops in my area still don't have enough knowledge on working on our cars yet. However, I will point my shop to this thread as it's by far the best when it comes to replacing a Bose vert system. Thanks again for starting this thread!
Carlos Chavez (JL Audio)
Jan 13, 15:26 EST
Hello,
Correct, you'd have to place the FiX-86 in line between the OEM amplifier and the aftermarket amplifier. Be aware you'll probably need to disable any Active Noise Cancellation in that vehicle as well.