It doesn't sound like you know what you are doing. You generally can NOT just take 'wires' from a car stereo and put RCA ends on it, to go to an amp. Speaker outputs on most modern car stereos are BTL. Meaning they are not referenced to ground and grounding one of the leads can damage it (most RCA shields are grounded on a car stereo amp). There is a converter you have to buy to accomplish what you are trying to do.
Why are you not at a local car stereo shop asking these questions and finding out what you really need to get this to work. Without burning something up.