KT150s in Audio Research Ref 110.

Did ARC say why the 150's aren't recommended?

They said the plate current is to high for the power supply I believe.

You’ll burn up the power transformer in time. You will shorten its life.
ARC power transformers are very expensive.

KT 120
Plate current 135 - 165 ma
Heater current 1.7 - 1.95 amp @6.3 Fil V
https://s3.amazonaws.com/tubedepot-com-production/spree/attached_files/ts-kt120.pdf?1382029860
~

KT150
Plate current 150 - 180 ma
Heater current 1.75 - 2.00 amp @6.3 Fil V
http://www.tubeampdoctor.com/images/File/data%20sheet%20KT150%20Tung-Sol.pdf

Exactly what I needed to see. Thank you jea48.  The Ref110 sounds awesome with the KT120 but I have 4 KT150 and was thinking about buying 4 more if the amp could handle the KT150s.