Ah, ok then yes you need 2 line level converters. One is for the Front Speakers, 1 is for the rear speakers. You will be using the factory head unit to send a signal to your aftermarket amp, the aftermarket amp will take front and rear rca inputs since its a 4 channel. If your amp has whats called "High Level" inputs, you can run the speaker wires from the deck, directly to the amp, then to the speakers. Make sense?