Found the cause! Since I compiled the last amarok with the debug flag set got some hints. Seems to have been NX related and have to do with name resolution and the correct value of the $DISPLAY environment variable.
Now output worked, but only for a few moments. When pausing sound in amarok it freezed and even when there ws sound quality was low and had a constant phweeeeee tone in my headphones like I had with slimserver when no sound was playing.

Bye, Val.