I wasn't going to respond. But Judy426 has to but her nose in where it doesn't belong.
You have an execeptionally large room with few reflection points. Not that at lower frequencies that matters. Remember you are dealing with 2 eights they are fast, tight, controled and will not give alot of air pressure espically at low volumes. Will they hit the lower notes shure. Will you feel those notes at lower volumes no. If bass reinforcement (for either air pressure or frequency response) is what you are after a good pair of subs may be the way to go.
You have an execeptionally large room with few reflection points. Not that at lower frequencies that matters. Remember you are dealing with 2 eights they are fast, tight, controled and will not give alot of air pressure espically at low volumes. Will they hit the lower notes shure. Will you feel those notes at lower volumes no. If bass reinforcement (for either air pressure or frequency response) is what you are after a good pair of subs may be the way to go.