The best RCA's i have come across is the "twisted pair" kind. Theese cables virtually get rid of all induced noise, most major manufactures make them. A few things to check out too. Make sure your battery is in good condition and fully charged. A bad battery can let through some alternator whine. A battery itself is a noise filter, a very good one too, and if its bad, you can get alternator whine in the system. I have an optima yellow top battery, and i have NO noise what so ever...Using a good quality shielded RCA cables too..