Not sure what to do about your factory system? You want to keep your factory head unit, right? I have found a piece that will allow you to do that and more. JL Audio has designed and built an interface that will process and control the audio from almost any factory-installed head unit without any major surgery to the dashboard. Basically, it takes any signal from your stock HU and processes it then, converts the connection into RCA and gives you 4V output. From there, you simply add your aftermarket amps and speakers and you are set. It even has an aux input for MP3, satellite or iPod. It does a lot more than I have mentioned, without going into too much detail, check out their website for more information that you may not want to know about it. It is called CleanSweep CL441 dsp. My local shop says it sells for $350. At first I thought that was way too much. But now I think it may not be too bad considering you would be looking at least that for a new head unit and all the other converters, etc.

Lemme know your thoughts and I'll try to answer as many questions as I can.

 

You could also just go with the much cheaper option of using a LOC (line-output-converter), which accepts the speaker wires coming out of your head unit, and converts these to RCA outputs. Less fancy I suppose, but does a fine job. Just a thought.