Be aware that many guitar amps are quite different than audiophile Amps. There is far more nuance to observe that just the power rating. Lots of guitar amps intentionally color the sound of the guitar input signal somewhere in the multiple stages between input to output.
Part of the fender Black face mystique and desire was for this precise reason. Each stage of amplification *can* change the tonal qualities of the guitar's output signal. The Fender amps did just that. And to the ear, in a very good way. Another quirk was that the tonal quality would vary with the volume levels as an additional "bonus". As there was no Master volume on these amps. Many discovered that to obtain the desired tonal quality, you had to have a different amp depending on the size of the venue, so that you could run the amp at the volume level needed by the venue and still get the tonal dynamic influences from the amp to get the "sound" you wanted from the guitar.
When CBS took over Fender, they installed some engineers that did not understand that, and proceeded to change the amp toward pure amplification (the audiophile perspective), rather than adding tonal qualities of its own. Most guitarists hated that at the time, as pre-effects between guitar and amp were only beginning to become normal additions. They couldn't get that harmonic rich and shaded tone out o the new amps, just the pure guitar output signal, which took some of the"life" out of the performance. It's a difficult thing to describe to those without the experience. The tonal nuances in a live performance from the amplifier becomes part of the instrument dynamics and interact with the artist as much as the instrument string feel and action. These things help inspire more "spiritual" performance by the musician. For a reasonable comparison, it is similar to singing a closet full of clothes to vs. a stairwell with its added reverberations. When it sounds better to the artist, they are more inspired to produce even better sounds than they thought possible.
Anyway many guitar amps are horrible audiophile amplifiers. The guitar frequency range is very small using only frequencies between 80Hz and 10,000. Other instruments can provide frequencies outside that range, and an audiophile amp must reproduce frequencies in the 20-20,000Hz range. While guitar amps can usually reproduce frequencies outside 80-10,000hz range, they may not reproduce a 20Hz signal and he same gain as an 80Hz signal. Same is true at the upper end of the human hearing range. @15K hz that piccolo, accordian, synthesizer, etc will have an imbalanced ignal strength reproduction across its sound output. Worse, yet that guitar amp may have quite a bit of added distortion to signals outside of its planned useful range. That piccolo may well sound like it was route through a Fuzz box @13K Hz. Audiophiles can't accept that. And a stage comparison would be to compare a PA system AMP to a guitar amp.
Audiophiles don't just focus on the main amp, which is certainly important. But the speakers are transducers that converts the electrical signal into sound waves. These too have reproduction idiosyncrasies, where some frequencies are reproduced at different conversion rates/efficiencies than others. They may also add distortion and their own coloration to their input signal, which is also the bane of an audiophile.
Do we need to mention room acoustic properties, where some rooms absorb a frequency and others will resonate that same frequency? Sensitive ears will certainly notice that!
