Ok, an update on the replacement of the fans. I replaced the fans with the 6K ones posted earlier. I was a bit impatient replacing the fans, and testing them on a running unit (just unplug the existing one, and replace it with a 6k one, and place it just behind the existing one outside the housing). I made a small mistake plugging fan #3 onto the header, but I put it one position shifted (so not all pins were attached), but this blew the header and pwm was not working anymore (fan almost did not turn), and gave a fan error. Luckily, unplugging the pwm wire fixed this, and the fan is now running at 6K and all errors are resolved. Sound level is a bit lower than the original 10k fans, but no spectacular gain (that is, with the lowering of the rpm's of the fans with the fae command). So all in all, happy that I did not destroy the switch.
But all in all, you have to be very careful replacing these fans...
