Greg at Volti used to do a little demo that was based on his work fixing older KHorns. He would just speak through one of the KHorn assemblies and then speak through one of his versions. It was a pretty startling comparison, the original sounded like his voice was coming out of a tunnel while his improved version sounds like his voice. I owned a pair of Forte IIIs and actually traded them to Greg as part of my original purchase of the Razz. He likes the Forte IIIs, as did I--but the Razz are clearly better and the Rivals are better yet.
That said, think the corner horns are really cool if you have the room set up and the space for them, but I imagine lots of folks don't. I've got some big spaces in my home, but not two corners that would work in any room big enough to accommodate them--at least not if I want to stay married!