Don’t know about moving from the from KT-88s to KT-120s, but moving from the KT-88s to the KT-150s in my VAC 450 Statement monos was unquestionably a significant leap forward in sound quality: much closer to real music.
Had a problem with the voltage regulator on one of 450s after the switch. But Brent Meyer with VAC did a great job of diagnosing the problem over the phone, and sending an assembly that was installed by a local tech without having to send the amps back to VAC.
Kudos to VAC for their excellent customer service!
Of course YMMV, but moving to the KT150s has my system sounding better than it’s ever sounded before in my room.
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