Chet, doubling up wire creates the equivalent of a a gauge three lower, e.g., doubling 16ga results in the equivalent of 13ga. No, there wouldn't be any significant benefit from this since 16ga is more than enough for a 15' run(see speaker wire table ). Also, unless the two doubled wires are in close contact, this increases the inductance of the wiring, with possible high frequency attenuation.

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Enjoy the music, not the equipment.