2004 kia spectra

thanks for the helpful info for my las post sparkie. 2004 kia spectra with stock infinity gold head unit and speakers. can i run a sub amp to the head and still be able to run the rest of the speakers to the factory amp?

Yes, all you need to do is hook up an inline level converter to your back speaker input wires the ones that plug into your speakers, that will provide you with a rca output from the converter, then plug a set of rca wires to the conveter to your amp, some of the newer ones will provide a remote turn on output to your amp.  Or some amps have a high level input plug that you hook directly up to your back speakers and will internally convert it to a signal in side the amp