Decades ago, coming from, or wanting to believe (because of cost) the view of “Stereo Review’s” Julian Hirsch, that all amplifiers sound the same (i.e., they're sonically indistinguishable) as long as the individual amplifiers were operating within their linear range (having low distortion, not clipping and having a flat frequency response etc.).
However, when owning an Aragon 4004 MKII amplifier (pretty darn good Dan D'Agostino designed amp in its own right), I trialed an Audio Research VT100 amp (100 w/ch vs my Aragon's 200w/ch, but tube vs ss).
Oh my, for the first time with the VT100, instruments sounded much more like the live ones I had the pleasure of hearing every day. That started me on an amplifier sojourn. I eventually settled on a Mark Levinson and later, a CAT JL1 and then, CAT JL3 and later an Atma-Sphere MA-1 (OTL) and a Pass Labs amp.
But even before I trialed the AR VT100, when demoing Apogee Stage speakers at a dealer (before I bought them), the audio store demoed them with amps that I (have now) forgot. What I didn’t forget, was the crescendo of a symphonic piece I had brought. Whoa, the drive and uncongestedness of the ending was something I had never heard! But because of cost, I delayed getting into the higher end amps.
As an aside, I’ve come to believe that symphonic music provides a true test of what components are capable. Yup, I’ve heard all of the “audiophile” vocal and intimate jazz recording etc. And they do well displaying what a component can do. But throw on the end of a symphonic piece (from a great recording, often like those found on Reference Recordings, or Chesky's) and assess the transition from soft passages to louder passages and as well, check-out the instrument separation and how congestion-free crescendos are reproduced for a true test of a component’s capabilities, especially amplifiers.