Asking a group of people if 37db is quiet will give you a whole range of answers. It depends on several things. The two most important are the hearing sensitivity of the individual and the background noise of the computer and the room it is in. If the environmental noise is already relatively high then 37db ain't bad. It may not be silent but it probably won't be obnoxious. If the environment is quiet then 37db may be annoying. For me with my ears in my computing environment I find that I begin to notice a fan's noise somewhere in the 32-34db range. One thing you might consider it getting a fan speed controller so you can adjust the speed (and noise) of your fans according to the need.
Another issue with fans is durability. What are reviewers saying about the durability of the Slipstreams?