I had to hunt a bit to find any info on the Unity Audio speakers, and in the process I think I found a link to your specific system on an old Audiogon forum post. In that post, you listed the range of the Fountainheads as 30Hz to 25kHz. If you have a subwoofer, I would recommend setting the fronts and surrounds to SMALL (which is required to apply bass management) and the crossover to either 40Hz or perhaps 60Hz - either could be appropriate, and whichever sounds best to your ear is the one to stick with. If you have a model number for the Dynaudio center, we could come up with a crossover or two to use for it as well. If in doubt, though, 80Hz is probably a good place to start with the center.

If you don't have a sub, all speakers except the center will be LARGE and the crossover settings for those large speakers won't matter because bass management won't be in effect. The center probably still deserves to be set to SMALL.