in the end i went for the Streacom F8B Case.
But it seems its out of stock in the EU, so that i have to wait until the end of july.
I changed the mobo a little bit, because the passive cooled case requires a specific board layout / cpu placement
they list suitable boards on their website
Did not build an AMD APU system yet but they seem to suit the needs of a HTPC quite well. I hope the desktop trinity models become more readily available soon. The A10 seems to be a good performer, maybe overkill for a HTPC.