to tame the bass bloat in my Harbeths when driven by tube amps
Sounds to me like its nothing to do with the speakers, or the room, and DSP certainly is not the answer. You're trying to make your tube amps have the same thin unsatisfying bass as solid state. I have a better solution: get used to it. If anything maybe try and figure out how to find SS amps that have as good bass as your tube amps.
I know. But you can always try.