I have an '04 FX4 with the stock sound system (stock sub too). So I guess this is the 'Audiophile' system?

Anyway, if I were to add an aftermarket head unit, would the stock sub still work? If not, is there anything that has to be purchased or done in order for the sub to still work?

Thanks!

 

Upon adding an aftermarket deck, your sub should still work. Most kits come with the sub out plug to plug to your existing factory sub. The only thing you may need to do is add a resistor to the remote on wire as the factory sub amp only requires 5 volts to turn on and an aftermarket unit sends 12 Volts. Its very easy to do. Just search SUB POP on these forums.