I'd suggest sticking as closely to the matched, full-range speaker concept as your room, budget, spouse, etc. will allow. All the standards organizations I know of, with the exception of THX, specify asuch systems. And while a good deal of surround production is still being done via "speaker-on-a-stick" systems, facilities are installing matched, full-range systems, seemingly, as soon as finances allow. So it stands to reason that the best results will most likely be gleaned from duplicating the environment in which the creative decisions were made.

That being said, do the best you can. I strongly suggest avoiding di/bipolar surrounds, though. I think that as more music is released in surround, we'll want diffuse surrounds less and less. There are always going to be those who see them as more than ambience channels, so who knows what will end up back there (as any veteran/victim of quad will tell you). So careful planning and acquisition now will significantly increase the longevity of your system.