The title really says it all. What I want is a maximally simple NAS that can take up to 4 3.5" drives. Literally all it will need to do is serve files over a 1Gbit SMB share. I don't need any other capabilities.
Since it will be close to my bed, I also want it to be SILENT. That means absolutely no fans whatsoever. The drives will be standard HDDs (not SSDs), so they should spin down when not in use. In addition, they should be fastened with soft materials so that the NAS case doesn't resonate and amplify their noise. In my desktop PC I've used the old trick of suspending the 3.5" HDDs with some sewing rubber bands in a 5" bay. That makes them practically inaudiable. I don't expect such amateur nonsense to be available in a commercial product, but you can at least put little rubber spacers between the drive and the case.