I am installing a low power single 10" system soon. I was hoping I could just plug the rca's directly into the factory non mach head unit. I now realize that there is no rca input in the oem headunit. I was hoping someone could tell me where the best place would be to splice into. or if there is an adapter for rcas to plug into that will go into the stock deck. This is an extremely low budget system so I don't want a new headunit. (free sub+box, 20$ used amp from friend, cheap 16$ wires off ebay)
its a 2002 gt

 

some of the systems will have a "high level input" on them that you can use to connect directly to the speaker wires. It is always better to get them at the source behind the deck, but it is always easier to get them at the rear speakers. I would try the rear speakers and if you have noise, try behind the deck. If this system has no high level input, you will need to get a line out converter, or loc.