Arctic Cooling Arctic Fan 12 $10 Newegg.com
Global Win NCB $8 Coolerguys.com
Scythe S-Flex 21E $15 Heatsinkfactory.com
iXtrema "11dBA" $25 SilenX.com
Cooler-Master SUF $6 SVC.com
Sunbeamtech Silent LED $6 SVC.com
Results first, comments later.
Quietest are the GW and the iXtrema, with the GW having a very slight lead. These two are separated from the other 4 fans.
The C-M and Sunbeam are tied for 3rd & 4th place
The S-Flex 5th
The new Arctic Fan 12 6th and last.
Rubber fan mounts were used for all fans. When I "set up" the test bed this morning, it became obvious that the test bed was too noisy and was obscuring the 'fan under test' noise. So I put a 3-diode "2V drop" wire in series with the PSU fan to lower its RPM, and I had to install Scythe anti-vibration HDD mounts on my #2 HDD, which had been hard bolted to a 5.25" external slot.
I turned the test bed - my #2 computer - around so the rear of the chassis was at the front edge of the table. This way, I could listen to the exhaust fan noise with my ear 2 to 3 inches from the fan.
I assumed that at the same RPM (1028.57), the air "whoosh" would be the same, and did not listen for the whoosh. I was looking for any other noise besides that, especially any mechanical noise of any kind. All I found (on 4 of the fans) was motor hum and very low-level sleeve bearing noise, a higher pitch. The motor hum was not annoying on any of the fans, and the low-level bearing noise was so low-level that it would be impossible to hear a foot away.
The test bed, while quietened, was not totally quiet. To make sure that I was hearing fan noise, I ran the fan voltage down to 6.6V and up to 11V, noting the change in the noise level. Any noise that didn't change wasn't the fan under test. I did this slowly, seeing if the nature of the fan noise changed over that voltage range. It never did, on any fan.
Let me say this again: at no time did I hear any bad or unpleasant noises from any fan.
The Arctic Fan 12 is a higher RPM device. I'll be reporting its RPM range separately in the Fans & Controller forum. To get to 1028.57RPM, I had to place a 3-diode "2V drop" wire in series with it. I believe this fan is best used where there's a need for a lot of cooling. It comes with metal screws that at first glance look exactly like the ubiquitous ones, but aren't. They're shorter and squared off. Don't lose the provided 4 screws if you get this fan. The fan has its own built-in rubber isolation mounts, and does have the tach (RPM) signal.
If what you're interested in is operating in the general neighborhood of 1000RPM, there's a clear winner in this group of 6 fans: the GW has the lowest noise and almost the lowest price. I've already received seven of them, and the low noise is consistent (no variance) in that batch.
On the other hand, if you already have any of the fans other than the Arctic Fan 12, you have no particular need to change. In a real-world chassis, with the covers on and the fan at the rear of the desk/table a meter away, all of these are quiet fans and the HDD(s), being closer, will likely be at least as loud.