Gary, this has been pretty well covered in the previous replies, especially noting Mr. Russell's excellent article, which should be studied if you haven't done so.

In brief, the slightly lower resistance of 10ga wire is meaningless compared to 12ga(or even the 16ga lamp cord I use)at the length used for main speakers. Minute differences which can be measured but can't be heard are quite common in audio.

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Enjoy the music, not the equipment.