subwoofer wire size

Hi all.

I have kind of a rather easy question, but a rather important one.  I was wondering what size speaker wire I need to use on a Kenwood 10" subwoofer that is a 4 ohm load and receiving 250 watts rms from a Kenwood amp.  The sub is in a sealed box.  Just threw that in there even though the box size may be irrelevant.  Anyway I know that the larger the speaker wire say 12 guage would be better but I guess my question should be what is the smallest wire guage I can get away with because I want to conceal the wire as best as possible because it will be going in my boat install.  I will be using Stinger brand wire which I believe is of very high quality. 

Thanks Much

Mr. Big