I usually remove most my interior, run the rca's, and speaker wire on one side of the car under the carpet, and the power wire and remote turn on on the other side of the car under the carpet.
If you bought a high quality set of rca's you might be able to get away with running them next to your power wire, but if not you should keep them as far away from the power wire as you can to avoid addind lots of noise to your system.