Mark, so the bottom of the TV screen would be at roughly 7' in that arrangement, and yes, the upward viewing angle would be a bit severe. Is the fireplace really going to be used, or can the TV instead be placed on a stand in front of it, more or less at eye level? If so, the tower speakers could then be placed so as to give an adequate separation of 7' or so.

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Enjoy the music, not the equipment.