I don't know if we're still referring to studio use, but it's mostly the
fan and drive noise, not vibration, that bug people.

Correct. The problem is also cumulative. The 24 port gigabit switch is
noticable but not really annoying, the NAS is noticable but not annoying,
the video editing station is somewhat loud but tolerable, etc, etc, but with
everything running, it's an annoying wind tunnel. My goal is to tackle the
loudest PC first, and then perhaps add more acoustic enclosures as needed.

Best,
Christopher