Going by specs alone a (apparently fairly easy load) 87dB sensitive speaker paired with a no more than ~8W 300B-based SET wouldn’t wring out the most of such a combo. You could no doubt attain great sound in moderately sized spacings, also at fairly loud SPL’s, but from my chair the real treat of low powered SET’s is using them with very high efficiency, preferably all-horn speakers (i.e.: +100dB sensitivity) where you’re taking advantage of the low distortion and ease of SET’s at fraction of wattages (ideally though I wouldn’t pair SET’s with high efficiency, high power capacity speakers with large diameter, heavy voice coils; these are better off with higher powered SS or tube amps). Driving speakers 15-20dB’s less sensitive - all things being more or less equal load-wise - will require up 100x the amount of power of a given amp, and with only so many wattages from an SET you won’t be using them at their best here. That’s not to say it couldn’t great to your ears regardless, certainly at no more than moderate SPL’s, but you’d be wanting for headroom.
