If this shows up as a duplicate post, please ignore. . .
My experience is similar to Charles. I have 101db efficient Zu Definition 4 speakers driven by an Ancient Audio 300b SET. Recently, the Ancient Audio amp required servicing; and I substituted an 80 watt per channel SS amp for a few weeks. The difference was noticeable, especially when I reinserted the SET tube amp. While listenable, the SS amp was lifeless and lacked tonal depth and immediacy by comparison. One curiosity (and I would be interesting in some opinions); I used the same, midpoint volume control setting on the pre-amp for both the SS and tube amps. The speakers are located at one end of a large (45' long x 16' high) open plan space; and I listen to a wide range or music from classical (chamber to full orchestra and chorus), jazz, classical rock, female vocals, etc.
Gary