I have searched ALOT but cant find my answer

I have a 06 Magnum SRT8 I have a factory amp for my mids and a aftermarket amp for my JLW7 sub. I really really wanna do the Car PC thing but I want to buy a prebuilt system with a 7" screen. My questoin to you guys is this: The car has Can-Bus and I have the PAC addaptor for the Kenwood Touch screen now. I want to take that out and use my Car PC for my audio/Wi'Fi/ Bluetooth/ ect. How is everyone geting audio from the PC to the car? I have found the FAQ on that part but it dosent answer my questoin. How do you get the factory wireing pluged into the Carpc since I dont have RCA's on a the factory amp?? Just my aftermarket Amp dose. Someone please help me other than teling me to search. Thank you