Have you gotten any responses about Kannenbergs from Prosen? I have my ggrandparents August Edwin Kannenberg and Wilhelmine Caroline Bottcher both being born in Posen and my grandfather was born in Allentown, PA. Now I have my gggrandfather David Kannenberg being born in Hammermaule, Bromberg, Germany and gggrandmother born in Schmukalle, Bromberg, Posen, Germany. Now I haven't done too much with research in Germany so I'm not sure of what the four places in my gggrandmother's birthplace means. I did at one time contact a cousin, but the address wasn't right for her and it got sent back. This was just after the Berlin wall coming down.
Hope this helps. Let me know if you have anything different.