I have heard these. I can compare them to my Triangle Magellan Cellos. The short point is this: they are way better than the Cellos. Compared with Canton K3 they are similar, but I would say the Cantons are better. There is not much between them so if you prefer the looks of the Sopras that would, IMHO, be enough to sway me. Personally I prefer the look of the Cantons so, for me at least, it is a no-brainer to go for the Cantons.
More to the point is that I have had a decent audition with the Magico A3s. Admittedly this is a different presentation from the ported Triangle - Focal - Canton style. I had the opportunity to upgrade to the Sopras: I dangled and lost that opportunity. But now it is the A3 or nothing.