What speakers are you using? As has been said, we can certainly do a custom sized pair to stack or the same with the Soffit Traps if desired. Many people start with either just sitting on the floor and then do a 'phase II' where a second set is added later on.
The Soffits do offer approx 40% more surface area as well as considerably more average/minimum thickness to reach lower into the deepest bass ranges.
Bryan