New to ARC amps is the internally designed auto-bias feature and ability to run 4-5 different types of output tubes on the fly.
I would have thought they would supply it with the KT-150 tube vs KT-120 given all the new Ref amps run on KT-150s but I am sure you will have an option to order it with whichever tube type you prefer.
Very cool and decent price point, although if the Ref 75 is $9K, it may have been better to come out at the $7,500 price point (matching the other Foundation series pieces) and maintaining a bit more spread to the Ref line.