[Alpine TSi]

I ran 10 gauge from my battery and fused it at 20 amps, I wouldn't worry about putting a switch on it as if your converter is decent it should have a switch already. Plus it is never really that good to break a thick gauge wire for the purposes of a switch, if anything use a relay to do it. I wouldn't run anything less than 10 gauge as the wire length would be too long for that amperage on 12 or 14 gauge.