Oh yes, I am very much an admirer of KLAVIERSTÜCK VI, and I think your description of it fits perfectly. Even the score is a beautiful think to look at!! The music is like speckled stars, little points of light. I cannot imagine how anyone plays it - it looks extremely difficult, with its tempo constantly changing ( and notated in a very unconventional way in the score). Can I ask which recording you are listening to? My favourite in all of the KLAVIERSTÜCKE is Ellen Corver.
I love Kontarsky too - but I don't think you would regret having both,and especially as Ellen Corver's set also includes XII, XIII, and XIV! For me Ellen brings a special, unique balance of poetry and power to her playing.
David Tudor's early recording is certainly a contender, even though it is not the final version of the score. In fact, this gives it a certain advantage for the newcomer to the piece, since its considerably shorter length makes it easier to grasp as a whole. Beyond that, though, Tudor's touch is absolutely exquisite, so that the colouration of his performance is unsurpassed.
I feel that it could be useful to have a discussion-forum on the music of Stockhausen. There are so many people from all over the world, young and old, learned and eager to get into contact with this musical world: musicologists, composers, musicians, music lovers; people who plan concerts - who write books or have to give lectures and so on. So there should be much stuff, many ideas that we can share. And when we have open questions, there may be people who studied just that and could give a hint or a stimulus.
A problem might be the English language, but i feel that is the only possibility that many people who are interested can participate. And we can exercise tolerance to mistakes!