I need an audiophile quality DSP with balanced connections (XLR / AES) to tame the bass bloat in my Harbeths when driven by tube amps.  I’ll spare you the details... but... just need a quality 
DSP with balanced connections.

There is no problem with my Hegel H590 or Class D Audio SDS 470C amps, just my ARC Ref 150se. So... it's not the room... its the amp.
You might know that I'm a tube amp manufacturer (that also holds a patent in class D amps as well). Take it from me on this bit (since the solid state amp is fine, we'll assume that a DBA isn't needed): speaker cables can affect tube amps a lot more than they affect solid state! So I have two recommendations: try several different cables and keep the cables as short as you can: under 3 feet if possible, and make sure the connections are tight. I would also try different taps on the output transformers of the amp as that affects things too- sometimes counter to what you might expect.

Yes... Ralph... I will try some of your suggestions.  I have your M60's and have talked with you about upgrades - though, I think mine have the 3.3. upgrades.  I'll try the 16 ohm taps and maybe the 4 ohm taps to see if that makes a difference with the ARC 150se's.  And I'm using Paul's cables, and have his Zeroformers, which I got for your M60's for my Maggies.

But, as you know... the M30.1's and M40.2's have a bit of an emphasis in upper bass / lower mids, which I resolved with some good SS amps (the ones recommended by Harbeth)... but... I think I may prefer the sound of the ARC 150se, except for the bass bloat that is not there with the SS amps.
Roon has the ability to run DSP through the output.  By all accounts this works very well, and at the price that Roon is, it is a very cost-effective solution.   Of course that won't solve vinyl issues.  And with CD would require the ripping and storing of the music.  But if you do play your music from a digital source and just want dsp with no pre-amp or dac then this would be the best solution. 
Roon... interesting... I've not used it and did not realize it has that feature.  That could be a quick and easy alternative, since my Bryston BDP-3 is Roon compatible.