@croissantfoxwine I know the Soul VI is a much more advanced speaker, but I owned both Tekton and Zu Soul Superfly speakers many years ago, powering both with low power SET amps. In my experience it is a real challenge to get a lot of warmth out of Zu speakers. The Soul in particular is a fairly small cabinet, and you have a medium-to-large sized room.
In fact, if you were to keep your amp and preamp, which George has already noted are really nice, you will likely have to invest in potentially bi-amping your setup, where the Shindo are powering 120-140Hz and above for a speaker, and you get more powerful amps for the lower frequencies. 8wpc in a room that size is very limiting if you plan to power the bass and midbass. But adding subs won’t necessarily give you the warmth you seek, as the Zu Soul are just not a warm sounding speaker.
Devore are definitely a little softer in their presentation, as are Audio Note speakers. Fyne Audio may also be another to consider. Horn-based speaker systems may be best, where the bass drivers are driven bi-amped with a cheaper Class D amp.
The rest of the community may have better speaker recommendations as it’s been a few years since I’ve done anything with low power and high efficiency.