Your mention of the Benchmark being under-powered brought to my mind this question:
I've often seen it said that some tube amps can "sound" more powerful than their power ratings suggest. FWIW, although my CJ amps are pretty powerful for tube amps, 140W/side (into 4 ohms), when I was going back and forth between it and a Bryston 4B3 (300W into 8 ohms - and up to 500 into 4 ohms per channel), the CJ seemed to keep up even when cranked pretty loud. That is tons of dynamics, punch, no sense of a loudspeaker running out of steam (Thiel 2.7 speakers, 87 dB, nominal 4ohms). Whereas I did get a struggling-for-loudness/dynamics when I have used certain older low powered tube amps.
Other people have talked about even lower powered tube amps driving even some tough speakers surprisingly well. I believe it's been suggested that various aspects of a particular tube amp's design, e.g. the design/quality of it's transformers, can influence these attributes.
Is there anything technically justified to this proposition that a tube amp with lower power than a solid state amp can in practice "sound powerful" like the SS amp, due to transformer design or anything else?
Thanks.