A good friend loaned me his Audio Research Reference 75 SE with a spare set of KT-150 tubes. This amp is monster to haul around. Bass is very good (tight) with the Ref 75 but there is not much sparkle on top like I enjoy with the ST-120 with KT-120s. Seems very generic sounding in comparison to the ST-120 though perhaps more accurate and less colored. The Ref 75 is more akin to transistor amps I have tried. I do though need a better balanced linefeed to Ref 75.
So the ST-120 happily lives on in my system. It has seen a few challengers in the past 4 yrs. but has held out and stands proud. Excellent amp Bob and great value!