RCAs next to power wire have nothing to do with noise. Run your RCAs wherever it's convenient. If that happens to be beside the power wire, so be it. Basic electrical knowledge will tell you the the slight ripple voltage on the power wire isn't going to induce any kind of noise in a simple shielded cable. It would take a large variation in current, not voltage, to create a magnetic field capable of inducing noise. No such current variation exists in your power wire. Additionally, if you have a good battery under the hood and nothing is wrong with your alternator, even the voltage ripple is negligible. The source of alt whine is differential in the ground between the head unit and the amp coupled with poor signal ground isolation. The system equalizes the ground differential over the RCA, introducing ripple noise into the system. If your grounds are solid and no equipment is damaged/defective, you will not have noise. You can go so far as to zip-tie the RCAs to the power wire (I have done so in the past) and it isn't an issue.