Last year, there were a few OB rooms. The Bastanis Prometheus, Emerald Physics CS2, and Lowthers driven by FirstWatt solid state amps.
I didn't see Bastanis listed on the exhibitor list, but the other two are there. I wouldn't be surprised if there was another room or two this year, since OB has definitely been gaining in popularity...
By the way, of the OB systems I heard last fall, the Lowther/FirstWatt were by far the best. That's the first bi-amped system where I've had zero reservations about coherency.
Haven't decided if I'm going back this year, but last year was a blast.
Regards