I just want to add that an untreated room by no means equal bad acoustics. Lots of beautiful recordings has been done in very lively rooms. As always, use your ears and learn to trust them.
Maybe not the answer you're looking for but I just want to add that any of these would be a very good choice of monitors, and you should make the final decision between them yourself. It all comes down to small differences between them, and it's your ears and preference of sound they gotta match.
I regret selling a 12-string electric Ibanez Artist, never played it much, but it was a beautiful and unusual guitar.
Also, I've regretted selling a Roland RSP-550 but bought it again, and same with the Marshall SE-100 speaker emulator, bought and sold three times lol. Also bought/sold and...
Personally, I rely on Seagate barracuda drives, as they have never been reported as having problems in the HD24. Except for you, which makes me think that once you get the vibration thing solved, stick with the barracudas.
Also, they are among the most silent drives.
A preamp would make a difference, but so would a LDC to catch some room ambience, or some other dynamics (MD421, SM7, e609 etc) for different textures. Hell, even a 2nd SM57 in a different angle combined with the first will give you plenty of new options and sounds.
If you're dead set on the...