I am very familiar with the sound of them, Justacoder and Jonathan and they are indeed that good. Part of the secret of their soundstaging is their excellent ion tweeter, of which I own a pair. There is nothing better on the market today. The A-capella make practically any kind of electronics you throw at them sound their best and with really good stuff they sound out of this world. I've seriously considered them already quite a few years back and then decided to stay with my wall of stators. The A-c have a much better holographic soundstage, which beats anything I have heard to date, but to mys ears they sounded just a bit too aetherial, too finely woven, too see through, which I found -compared to live music - to be an artefact, which though is very kind to CDs. So, being a vinyl-man, I stuck with my stators, which I found more "real", though greatly improved in highs and soundstaging by the ion tweeters.
By the way, Jonathan, I quite agree with what you heard, they can develop slam however....teamed up with Jadis 200's
(the four chassis job) and the Jadis 500 amp as I once heard them, but even then, there was something subtly overdelicate about them, you could practically "touch" the players, so three dimensional it was, but the players were holograms, not "people". You only very rarely get that with stators, that feeling, that the players are with you in the room, but if you get it, it sounds uncannily like real people and real music.
Next to the Campanile and the Violon they also have cost no object offerings ( vide www.acapella.de), which are also, as Jonathan rightly remarked, very easy to drive.
Their sound characeristic has the same see-through quality together with a bass rendering, so precise, defined and DEEP, it can scare the sh;;s out of you.....