DSP TO TAME THE BASS IN HARBETH SPEAKERS

audiophile quality DSP with balanced connections

https://www.deqx.com/products/premate-plus/

http://www.accuphase.com/model/dg-68.html

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.

Won’t comment on if you do or don’t need a DSP. I’ll leave that to others who seem to know your system better than you do! ;-)

I just integrated the DDRC-22D into my system and for my room, my limited ability to treat, and my configuration it was probably one of the best additions ever. It just “brought everything” together. 
I believe the ability to tweak the response curve was a definite improvement, but the adjustment to the impulse response probably made the biggest improvement, noticeably to the soundstage. 
Good luck!