I am now experimenting using a Stage 4Pi setting on top of an Adire Rava subwoofer as a center channel for home theater and as a center speaker in a 3 speaker "stereo" played through my AV receiver. I have to say that this combination is pretty impressive. I think the Stage 4 Pi sounds better off the floor a bit. Using a subwoofer and crossing it over at 60 or 80hz makes a really dynamic full range speaker and is great fun to listen to. If I were going to make a stereo pair of floor standing speakers and had the room size and suitable location I would make a pair Pro 4Pi's with JBL drivers and a subwoofer such as the Adire Rava or Tempest, the Vmps, GR Research or PartExpress Titanic in one large cabinet with separate chambers, or two cabinets with matching veneer. The whole cabinet could be less than 44" tall. By putting the sub with the Pi's you get the Pi's off the ground about the right height, you can cross them over above 60hz if you want without worrying about being able to identify the bass as a distinct sound a part from the rest of the speakers, phase issues also don't exist. Using two subs may give you smoother bass and will certainly give you more of it to help the subs keep up with the dynamic range of the Pi's.
Larry