I was wrong about the phase cancellation. Evidently when I hooked it up with cables from the left out and right out into two channels on the Bose, I was using stereo cables (balanced) and that was causing the problem. I had a mixer in between, and somewhere along the line signals were getting duplicated.
Tonight I hooked up two unbalanced cables into two channels on the Bose and heard nothing but good stuff coming out.
Sure wish this G70 thing didn't weigh so much. There's a lot to like about it.
DonM