Thanks for the kind words, but I think you overestimate my knowledge. Yes, indeed, I know several systems that are or should, in theory, be adaptable to the Pentax 645N. And yes, by coincidence, I've tested several lenses from the pentacon six system to a degree that I am confident, that they are not the kind of lenses I am looking for. But honestly, this is about where it ends.
I phrased the question in an open manner because I wanted to get feedback especially from users of other systems about positive experiences with prime lenses in terms of bokeh performance. My replies were not indented to show off but to give the posters an informative answer about why I do not indent to pursuit their suggestions. If I have choosen the wrong words, I apologize. Please consider the fact, that english is not my native language.