I have had some very expensive multi-way speakers and when starting to design my own I saw some single driver speakers, so I bought a pair of 8 inch alnico Audio Nirvana drivers and had a cabinet builder make cabinets using the design shown on the Commonsense Audio website. The alnico magnet drivers had a much smoother frequency response that that of ferrite and neodynium magnets. I was completely taken aback with these, especially when mated with my JL Audio subwoofer, which completes what I consider the only real achilles heel of single driver speakers: bass dynamics. They can certainly plumb the depths but cannot move air like real woofers and subwoofers. So I then sold these and bought the AN 12 inch drivers and a larger (5.6 liter versus 2.8) cabinets, and they are a significant step up in most parameters. As far as treble, after hearing these I wonder why anyone makes tweeters, even approaching the sound of the ion tweeters in a pair of Acapellas I once had. And the midrange is simply unreal, as well as soundstaging and immediacy.
I unfortunately cannot answer your question about the low-powered tube amps you mentioned as I use as powerful solid-state amp and a tubed preamp and phono stage. I would think the tube amps to be a good match with the high sensitivity and easy load of the speakers. Remember, your amp is driving the speaker voice coil directly, and IMO, I can hear what multi-way speakers with crossovers do wrong.
