Orienting vertical speakers horizontally affects the dispersion unfavorably and should be avoided if possible.

My thought is to not be too concerned with the listed specs on a sub's low frequency extension, which will vary with each room and the position in the room anyway. Any of those which have been mentioned should be fine and my view would be that if you could spend more that it would be better to spend it on the main speakers.

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Enjoy the music, not the equipment.