You'll need a line level convertor to convert the speaker signal to line level that your amp input needs. Unless, your amp has speaker level inputs as well as rcas that you can use as an input. Most amps do not, though some do. Even if your amp does, it's better to convert it then use a speaker level input. Don't forget to run the amp remote turn on lead from your head unit to the amp as well. This turns on the amp when the stereo is turned on.