Has anyone ever connected an aftermarket amplifier to a Premium Ford sound system in a '98 F150? I was wondering if I could tap the speaker line at the speaker and add a line level converter in order to provide RCA inputs for the amplifier. I don't want to change the factory head unit or to remove the factory amplifier (wherever it may be). I would just like to add a 10" sub under the rear seat.

 

You can buy amps to hook up to factory Head Unit. They have speaker wire hook ups on them. Check out CRUTCHFIELDS.