Simplify things and get a second, separately amplified unit for the bass. OR get ready to work on a transmission line/ back horn/etc AND even there, you'll have trouble getting the phase right. There are available plans for cabinets around the Jordans (good designs) -- as Audiokinesis suggests. In fact there are good kits available; try Hammer Dynamics for one.
Fertin & Supravox and Phy offer excellent (~8" units) but they are very expensive. BTW, Laurentgilles above means Hertz obviously -- not kHz -- when referring to a 15" unit on an open baffle:)
Fertin & Supravox and Phy offer excellent (~8" units) but they are very expensive. BTW, Laurentgilles above means Hertz obviously -- not kHz -- when referring to a 15" unit on an open baffle:)