The Boston Audio Society did some wire tests c1972 and found that 12 GA zip was best in that it offered the minimum of both inductance and capacitance per foot when compared to either heavier or lighter wire. You might find this article at the BAS site.........?

I do not spend significant bucks on wires.... I attend live recitals and as long as my system continues to match the live recitals I will see no reason to worry about wires except that they are "there" and "functioning".