So for all the readers who were curious what happened to the top-level domain that I recently wanted to sell. Here the final result: I sold it for $60000. I think I could have gotten more out of it, but the sale wasn't solely for money. I wasn't excited about this niche site/business and if you are not passionate about it, it makes sense to sell and let somebody else build something with it. Even that I own a bunch of other great domains I never wanted to be one of these "domainers", who waste the time of all these people, who were looking into valuable information and ended up on a... let's say mediocre website.
Also I am happy about the new owners, who will use the domain in a better way than I ever was able to. At the end it's for all a great move. Including the visitors who now will get quality content.
Update: Darn. Sale fell through. Well...there are other people who bid even higher.