Well.. I've got to tell ya; the Counter-Current Tunze skimmers seem to be the quietest; but not the cheapest, or most efficient.
Needlewheel are second, the Deltec Eheims are the quietest, and probably the most efficient, but also costly. The ASM NW is a little noisier, due to the Sedra Pumps, and honeslty, the Euroreefs are close enough in design to the ASM to not make the difference in rpice worth it. They're close enough in cost to go with the Deltecs, too, to get rid of the Asian pump, and get a solid Eheim.
I run a Beckett on my system. The skimmer itself is quiet. The pump has fan noise, but overall, I still think it's quieter than my old Remora Pro, and it's moving A LOT more air and water. Great skimmers, as long as you don't mind paying for power.
Airstone skimmers are pretty quiet, but require upkeep. Changing stones, etc.
If sound is your only concern, go Tunze. As far as Needlewheel vs. Beckett, it's gonna be a person-by-person preference. I love my Beckett, and had pretty mixed feelings about the ASM I had before it. I'm sure there are just as many in the opposite camp...
I just ordered a Tunze NanoReefpack 200 for the 29G Leather/Softie aquarium in my Bedroom, for sound reasons, I'll keep ya posted as to how well it works when I get it...
-Andy/Oldimpala