I would pay to hear them in a direct comparison. My impression from what I've heard is twofold, firstly a matter of "missing the forest for the trees" (= i.e. neither DAC is perfect, but it is no secret which errs on the side of missing the forrest rather than the trees and vice versa), and secondly, that the beautiful-sounding Kondo actually has a sonic signature, one might even say a memorable one at that, whereas that of the Vivaldi becomes awfully hard to pin down in words once one has heard it in a variety of systems. I have much more experience with different dCS models than Kondo, and of the other usual suspects, I got a chance to listen to a number of Lampizator occasionally, yet e.g. MSB, Playback designs etc. only occasionally - so one would think I should be more qualified to describe the sonic signature of dCS better than people who occasionally hear it in unknown systems at trade shows, instead of a number of systems they know and lived to hear evolve over the years, compared different components in etc. & etc. And yet, I find it most difficult to describe the sonic signature of a modern dCS DAC (especially following the Version 2.0 hardware and software updates). They've continually evolved into the direction of leaving a lesser signature of their own, so that in the systems I know, it becomes increasingly clear that whatever minor flaw one might attribute to the source, one will have to find elsewhere in the system. To pour less or no chocolate sauce over said flaws, they really tend to stick out like a sore thumb. Which is why I said earlier that taking this path may lead to frustration and I wouldn't recommend it (the handful few to whom I would recommend it incidentally tend to be the ones that wouldn't heed my advice in the first place).
To put it differently, I know at least three dCS owners whom I told about our Lampizator weekends, and who couldn't be bothered to audition one, whereas I appear to be the only one in our local circle of audiophiles who finds something (admittedly different) to like about dCS, Kondo, Lampizator, MSB, Playback Designs (if only the DSD playback there) etc., but then, my priority is music and the sound of music, plus I may have an easier time as I don't have a horse in this.
Greetings from Switzerland, David.