@Digby in the sense of lo; quality, speed, endurance. I have WD Red which whosent my first choice but I hardly heard it before without anti vibration month and don't hear it at all with it. 20% lower performance compared to Black/Gold is not an issue. Where I live ambijent noise is very low so even a quiet hum is audible which usually shouldn't be in noisier environment.
Your thinking may be outdated regarding 2.5" drives. I can understand it, there are a lot of 2.5" HDDs that saw laptop use as the main drive before SSDs became available (10+ years ago), and they were really slow, say 20MBs speeds, all while running the OS too!
The new portable 2.5" drives can easily do 140MBs sustained writes. They connect by USB3 and have some lag when waking up from sleep (they tend to sleep after about 5 minutes), other than this they are as fast as the WD Red 3.5" I have from about 5 years ago, faster random access actually, but much quieter.
Jury is out on longevity, but I always have multiple copies.
As stated before I am satisfied with colling capabilities achieved and it's not really noisy but it will never be completely silent either
You could probably make it quieter, but at some cost. It seems to be a fair way from you, most PCs are within about 2 or 3 feet, yours seems further away, any noise will be less troubling at a distant.
A truly silent pc has no moving parts and an expensive "case as heatsink" system (may still have transformer/coil whine though!). Nowadays, when fans are generally quiet and CPUs have quite low power draw (anyone remember the 3.2ghz P4!), it is far cheaper & easier to use a fan or two, running slow enough that they are inaudible (different from silent) from say 40cm away.
I think it is all about getting a sensible balance, depending on use case.