I removed the fans in both of my A4000 PSU's (liteon and skynet) and replaced them with SWiF2-800's with rubber grommits which made them almost silent with "almost" the same CFM airflow as the original.
http://www.quietpc.com/cl-swif2-800I was a bit worried that the airflow might be less with them being so much quieter but I've not had problems.
