I've installed some 12" subs & aftermarket 6x9's in my car, but had to splice into the rear speaker wires to do so because I'm not going to spend $300 on hardware JUST to install an aftermarket head unit. My question is are there RCA outputs on the back of my stock stereo to run to an amplifier?

 

typically no, but you can buy line out converters pretty cheap. most stereo shops have them. ebay, crutchfield, maybe even summit.