If you are going to use these outdoors or in very large rooms, you might not want an overdamped curve, maybe prefering even slightly underdamped. If you increase cabinet size to say 10ft3 or 12ft3, maybe also increase tuning frequency to 35Hz, you'll increase output around 30Hz. I would only recommend this for outdoor use though, or for very large rooms. In a small to medium size room, the larger cabinet may sound a bit boomy.