I have the PC-68, purchased about a year ago - the fans are Adda's, rated at 31.4 CFM, 28.3 dBA. AFAIK, they haven't changed the fan - at least, Adda doesn't list any fans that have the proper specs to replace mine on their site. Like others have said, they're quiet, but not the quietest you could get. I always ran mine on Medium, except in summer heat waves, since I found the high setting did little for cooling and was noticeably noisier. Recently, I took them all out and replaced them with Vantec Stealths (27 CFM, 21 dBA), which were just a bit quieter at full speed, and then ran those from a fanbus to reduce the speed to about 70%, which is fine for my system.
If you're starting from scratch and are concerned about noise, I'd recommend sticking with the Adda's, but using a fanbus to slow them down when not absolutely necessary - the Vantecs I bought were not worth the price for the small noise reduction. The airflow in the LL's is awesome, so unless you're seriously overclocking, the three case fans plus PSU fan should handle the heat just fine.