Ill start by saying, I am not an expert in any way when it comes to audio systems.

I have a 2006 screw lariat. The stock head unit has been replaced with a pioneer Avic Z1 updated to a Z3. I have the Ford subwoofer under the rear seat and I'm assuming the small box attached to it's underside is a small amplifier. If so, do they make a converter cable to switch from the Ford factory harness to an aftermarket amp? If so, I'll swap amps and possibly upgrade my speakers.

Any information would be greatly appreciated.

 

You are correct that the small box is an amplifier, for the subwoofer. The door speakers are powered by the head unit. It's easy enough to replace the speakers, of course. I replaced mine with Infinity Reference 6830cs in the front and 6832cf in the rear. Connections are easy with the Metra 72-5600 speaker adapters.

I don't recommend powering the factory subwoofer off an aftermarket amp; I think you're inviting problems for very little benefit. If you're replacing the whole factory sub assembly with an aftermarket amp, sub & box, that's a different story; get the Metra 70-5521 or Scosche FD23B harness. That harness can also be used to power the door speakers off an aftermarket amp. Connect the HU's preouts to the amp with RCA cables, then run speaker wire from the amp back to the harness, which will route the amplified signal back to the speakers.

My setup includes a Pioneer AVIC-X920BT powering the Infinity speakers I mentioned above, and the factory audiophile sub, connected via a Scosche FD23B & Axxess AFDI-5V. I have an old Alpine V12 amp that I may eventually use to power the door speakers, but for now, they sound fine running off the Pioneer HU.

 

Thank you very much for the information. I'll probably end up flipping a coin to decide whether or not to upgrade all the speakers and amps or not. I have the amps, but I would have to invest in new speakers. Again, Thanks!!!