yep changed the fans nice and easy removed an old one because its "engine" seemed to have gotten messed um somehow.
its running much more silent now
Silverstone fan, FN181-BL, 180x32 : this one i had to cut of some of the plastic because its 10mm higher than the standard, in my case the mobo didnt fit. and i think this pulls a bit too much air (fan silent, airpull noisy). Found also out the info about 120mm fan slots on the factal design xl is true but not good idea, somehow the same 120mm slot actually also fits 140mm. in this case if you buy a 120mm like me you will experience noise because of the airflow. thats how i understand it now.
i did the mistake of buying because i didnt look into the cabinet i used fractal design info page -.-