I can't speak for the Von S's (though I've read good things) but I can also speak for the Sonatas (I have the II's too) as they are exceptionally musical. They are easy to place but do appreciate the extra effort to get it just right. Never fatiguing and extremely flexible to your choice of power as they are an easy load for SET's (and sound phenomenal on vocals/midrange) while also cranking out any kind of gusto you want with high powered tube or SS. The Sonata III's I believe are a little less efficient at 93db but still excellent, as above, while my II's are 95db and rated for 10 to 1000 watts... who else has such versatility? From jazz to classical to female vocals to some good classic AC/DC and the Cult; I run SS into mine sometimes for slammin (older Rotel monoblocks that sound fine on most rock and roll recordings) , switch to tetrode tubes for most "normal" listening (my VTL monoblocs) , then to triode for "rich and creamy,etc". Looking for a low powered SET next, maybe 8 to 10 watt "300B" based or possibly 15 to 20 watt or so "845" based...( my preamp has 4 pairs of main outputs... I just have to play with speaker cables for a minute ot two) -all with the same speaker! Very satisfying. Listen, and good luck.