If your sub is 4 Ohms, the wire is more of a factor that if it's 8 ohms. You might consider 12 gauge wire. I use 14 gauge solid (twisted) for very long auditorium runs with no problems. There is flat, 50 conductor computer cable on the surplus market (65 cents/ft. in 100 ft. reels) that will be undetectable under a rug. It's ugly, but who needs to see it? Use 25 strands for plus and the rest for -.