You might want to add shotshop to your list. They are midstock (30 Euros per image, regardless of web or print). There's a monthly upload limit that starts with 30 images for new photographers and changes according to your acceptance rate. I haven't had any sales there yet (only started there 8 weeks ago), but from what others say they seem to have regular sales. I like the site a lot, I must say. Whether they accept English keywords, I don't know. But I don't think I'd recommend keywording in English if you're trying to reach German Buyers - wouldn't rely on any site's automatic translations (maybe except for istock. Otherwise, as you probably know, fotolia is the leading stocksite in the German speaking countries.
Otherwise, I can't think of any other German agencies that are not on your list.

There is also http://www.imagebroker.net

Photocase belongs on this list too: http://www.photocase.de/

Hmm... How is the translation with Panthermedia? My view are very low there - no sales. The translation could be one of the reasons.

I added the list of German stock agencies to my resource page http://photo.hlehnerer.com/Resources.html#StockPhotography with a link to the Alexa Traffic Rating.  Some of the statistics don't look to bad.