Hey,
It depends on your amp,
Does your amp have a "High Level Input plug?"
In other words does it have an input other then RCA's? Its normally a sqaure or rectangle plug on the same end of the amp and the amp normally comes with this plug also, Though im not sure if late model amps come with them anymore. Otherwise you can buy an adapter from Jaycar Electronics or a electronics store that converts the high level input plug into an RCA plug! 
If so you can connect the amp via that way to your headunit. As it will not have RCA outputs on your headunit so you can connect the amp via the speaker outputs on your headunit. (Which will most likely mean you will have to disconnect your back speakers - correct me if im wrong, otherwise the ohm load will be to low on your headunit and you will damage it.
So i dont confuse you this is what it all means: :P
What are high level versus low level inputs for an amplifier?
An amplifier needs an input signal to amplify. A high level signal is the signal that plays through speaker wires. It is called high level because the signal has already been amplified. A low level signal is what runs through an RCA cable like found in your home stereo. Many amplifiers can accept either or an adaptor can be purchased to adjust the input accordingly.
Aftermarket radios often have RCA signal outputs, which can be plugged directly into an amplifier. If you'd like to hook up an amplifier to a factory radio or radio without RCA outputs, you will need to purchase an amplifier that can accept a high level input or purchase a line level adaptor.
Hope this helps,
Cheers,
Scott
Panther Mica VS Commodore
HP Design 18" Chromies, Lowered, Extractors/Exhaust, Cold Air Intake
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