Now I can answer from specific experience, because I just picked up a pair of Sonata II's today. Holy moly, as my brother says. They are absolutely incredible. The person I bought them from had the Sonatina II's and said they sound quite thin in comparison. That was also my experience when comparing the Sonatina III to Sonata III. The Sonata's were engaging, while the Sonatina's were distant.
The Sonata II's are extraordinary. The drums have so much body. The vocals sound like they are floating in the room. The key for us was playing around with the interconnects. If the IC's are too muted on the top end, the speakers sound bass heavy and unbalanced. We put some silver IC's on, and pure magic. The speakers disappear in the room, and we cannot stop listening to them!
With our 7W SET amp & with a 40W hybrid, they are simply awesome! Back to the music....
Howard