Martian

yes, you could use one wire for the positive, one wire for the negative. I have done a simple test with that. I had one speaker double wired and another single wired, and there was a difference, but only on wire that was very thin (22 ga).
With 16 ga wire, I don't know if doubling it up will make a difference. The best way to find out is to try!

let us know how it turns out!