Ron or Tom, Just received my PB2+ last week and I love it. I will probably be purchasing a second one early next year. This is one solid enclosure. Can they be stacked one on the other? I want to tune them to 16hz and two ports plugged. With two of them, I should have little fall off on the high end db level. Stacking them would save a little room. It is feasible? Or would I be better off just purchasing the B4+? Would 2 PB2+'s outdo the B4?