Robb, re 6.1 vs 7.1 if any back speaker at all is going to be used, my view is to go with the full benefits of 7.1. Although there's no 7.1 material as such at present, applying DPLIIx or Logic 7 to two channel or five channel material results in different "stereo" material being steered to each of the two back speakers.

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Enjoy the music, not the equipment.