Adding more to Sun and Sound package?

I have an 09 Lancer GTS with the Sound package (650w amp). I have an alpine amp and 12" JL sub from my RSX I sold. I have searched for folks who may have added onto their current stock setup and have only found requests for wiring diagrams. I would like to know if anyone has actually done this and documented/took pics of it? I know I will have to run power from my battery to the alpine amp. I would just like to know exactly how to pull the audio signal and remote start from the current RF amp. I also read somewhere that a digital signal is sent out to the RF amp, is this true? Is there some sort of converter I can purchase to splice into the signal coming from the HU to the amp telling it to turn on and giving it the audio signal? Any help is appreciated.