Is there any advantage to increasing the gauge of the power and ground wires to my new Nakamichi CD-400 from the stock harness wiring of approx 18 awg?
it depends if you are going to use the internal amp of your hu. i'm not sure about your harness, but the power and ground wires are usually larger than 18 guage, but around 14 guage. if your harness has 18 gauge for the power and ground, then you may want upgrade to prevent a short. if your power and ground wires are around 14 gauge, you may not see a difference since the hu is designed to work on stock wires unless stated.