I've been thinking of a variation of the Dick Olsher Basszilla, by using an active crossover I can make a cheap bass-bin and use a small open-baffle with the 208 on top. Problem is cheap bass-bin may not match well for the dynamic and fast full-range driver. Costs and space are a concern otherwise I would get the same driver Olsher uses, an Eminence Magnum 15HO.

But if I spend that much money, I might as well buy a kit that has been well thought out so that I can get good results from the beginning. The 4Pi looks to be best bet, although the large 15-inch woofer has me concerned about how it will sound in small rooms of 12 x 12 or 15 and variations of that common to most houses.