You could use 18 awg, 16 awg, 12 awg, 10awg. It doesn't really matter unless your amplifier is an extreme distance away from your subwoofer. You will see no benefit using 10 awg vs 16 awg. Again, for speaker wire, it doesn't make a measurable difference using OFC or CCA. Use whatever you would like. If your wire burns up, its too small. Otherwise it's completely fine. Mistake me if I'm wrong, but more heat creates more resistence, in a dumb down version yes?