Reply To: some hints on how to proceed?

@ Martin

That sounds like it would work. Unless you have a specific layout desired for the categories, the Enhanced Category extension (which you have) has a shortcode that can be used to output the categories. Then you can achieve what you want with only two pages. One with the categories and the other with the directory which would only show the results of the categories that was clicked. Doing it this way, you would have to disable the category dropdown in tile Plus so things do not get confused.

Hope that helps!