Mike,
Great job on the new design. The GAS crowd got to hear them at our most recent gathering at Rick's house. Bryan had them set up in one of Rick's spare bedrooms.

As I understand this was pretty much the same setup you and Bryan (bpape) had out at RMAF with the big Korato amp, KVP-10 pre and a Bolder SB3 and power supply (GIK traps of course). For such diminutive speakers, the little Sapphire XLS' have a MONSTER sound. Nice, clean and even, top to bottom with killer low extension for such a small driver. I didn't do any measuring but I'm guessing we were in the mid-to-low 40's in that room. Not much need for a sub when they dip that low. That particular pairing of gear threw off a very nice soundstage with very good focus too.
Needless to say everybody was pretty impressed with their sound.