MJ, any piece of metal that has adequately low resistance, considering the length of the run, works as well as anything at any price. Even if your friends swear that on a stack of bibles, they're deluding themselves and could never identify a difference in a controlled blind test. If you have the typical length of run to your M60s of ten feet or so, then 12ga is more than good enough and is a bit of overkill.

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Enjoy the music, not the equipment.