Thanks for the compliment Philip. Having heard the ref 150, 250 and a 610 fitted with kt 120's I cant help but think that ARC has somewhat reverted back to a more classic tube sound. That typical 6550 slight upper mid glare of previous ARC amps is gone, banished. At the same time, images are denser, tonal colors more fleshed out. These 250's are the first amps I've tried that really seem to fully control and extract the difficult Mini's potential. It's almost unreal how a two way can pressurize a close to 500 sq/ft room driven by the ref 250. But as I earlier pointed out, I definitely hear a pervasive tube like warmth and bloom, a trait that I really like so I'm hoping that these amps' sonic character don't radically change as it approaches ARC's claimed 600 hour break in period.
Did you compare the REF250 with the REF610 fitted with KT120s and/or 6550s?
I once listened to a pair of Minis driven by REF610s and also could not understand how such small speakers could fill the room in such a way. Any one not having experienced it will tell us we are fools ...