5560
I have the SIT-3 (18 w @ 8 ohms), and the Audio Note AN-E/SPe HEs (sensitivity 97.5 db, impedance 6 ohms for most of the audible audio bandwidth).
I find music from this combination to be viscerally involving, totally satisfying, and very revealing. In "I don't believe in you," by "Talk Talk - The Colour of Spring," the bass is deep and resonant, the plucking of guitar strings is clear, and at times resonant, the vocals and treble are crisp and distinct, and the separation and depth make the music 3D. Similar to Herb Reichert's description in his review of the XA-25, for me the SIT-3 is very transparent.
In your search for a proper speaker match, I think a good place to start is Herb Reichert's real world review of the SIT-3, which compares how the SIT-3 sounds through different speakers. Here's a link to Herb's review of the SIT-3:
https://www.stereophile.com/content/first-watt-sit-3-power-amplifierThen I would read Herb Reichert's review of the Pass Labs XA-25, which contains related comparisons. Here's a link to that review:
https://www.stereophile.com/content/pass-laboratories-xa25-power-amplifierHere are links to other reviews that I recommend:
https://www.6moons.com/audioreviews2/firstwatt5/1.htmlhttps://positive-feedback.com/reviews/hardware-reviews/first-watt-sit-3-stereo-power-amplifier/https://parttimeaudiophile.com/2018/07/15/review-first-watt-sit-3-amplifier/https://www.youtube.com/watch?v=zeU4AEq_5UcThere is so much information in these reviews that I had to take notes. As an owner of the SIT-3, even if you've already read these reviews, they are an interesting read.