Some 10 years ago I had a pair of 150s with cryoed input and driver tubes (6550 and EL34s). I ran them balanced using Silversonic ICs, underneath was Stillpoints and Risers and Harmonic Resonance boards made with violin wood. Preamp was a tubed Lector, special ordered as true balanced, and a Raysonic 168 tubed CD player with NOS tubes.
The amps transformers were not the greatest, producing rolled off the highs. My friend at the time sold audio tubes and heard them stating the problem was their transformers. You should find out if they've been significantly upgraded
hth