The Mentor is not that intensely warm as the Aune S17. Still it is class A and Class A is not only about warmth
The Mentor might not be that impactful or super dynamic but it has a bass that excels in control, layering, nuances, definition and refinement. The S17 can't hold a candle in bass quality.
The S17 is a bit more meaty and visceral but there is much more to the sound than these qualities. Still for more meats to the bone go for the Aune.
Of course there are other qualities to the sound, like transparency, fidelity, resolution, clarity, refinement, timbre etc, that the Mentor outperforms the S17.
Don't get it wrong, the S17 is one of my favorite amplifiers ever but the Mentor is on another league.
It's good HiFi vs High End
Simple.
Thank you for your honest statement, but personally I don't like to pigeonhole things as Hi-End and all the rest. My experience tells me that what is much more important is the combination of components in the sense of synergy in relation to a specific taste.
I see more and more clearly that Mentor is not my pair of Wellington boots. Currently, I am looking for items such as Hifiman Prelude, Violectric V281. I am collecting data, but I see that it is all a matter of certain compromises. You get something, but you also lose something. What @Majuto writes is also very close to me, it's very good to have several amplifiers.
The obvious advantage of Prelude is that it is available and I can return it, which unfortunately cannot be said about Mentor, where returns are excluded as far as I know, and we have already written about availability.