umm...im still going to have to disagree with everyone about stepping up to larger guage wires. theres no reason for it. speaker wire is an a/c circuit independant of the 14 or so volts d/c that runs the rest of the car. theres a much higher voltage level, so the amperage can be decreased (ohms law power =volts x amps) to make the same amount of power. even with 16 guage wire, you are good up to many thousands of watts without any audible difference, because the total resistance of the wire will never go beyond about .1ohms. besides, the inefficiency of the speaker itself is so overwhelming that speaker wire is the least of your concerns. also, even the thinnest speaker wire will not cuase distortion. its not possible. distortion is a property of the output wave from the device, not of the cables.

go here for a good speaker wire calculator:

http://www.eatel.net/~amptech/elecdisc/speakerwireselectorassistant.swf