Which Schitt Audio Equalizer operates as a loudness switch for low level listening

An EQ can help your situation. A "Loudness" button generally adds a lot of bass and a little treble, creating a "smiley face" curve. The equalizer will let you add some additional high end if that pleases your ears. The Lokius should be fine for that. 

I recall you were asking about speakers that sound dynamic and full at low levels. I think you would find JBL 43 series monitors will do that. 4367 or 4349 or even vintage 43xx speakers if you can find them in original condition.

Ask Agon members who have those speakers. There are at least a few.

If you always listen at low levels, have you considered turning up your subwoofers?

I have a Lokius. I bought it with the idea of equalizing old vinyl, but after upgrading my vinyl playback system, I didn’t feel that I needed it. I barely used it, but it seemed to work fine. Wasn’t noisy, etc.

I don’t like introducing another component and cable in the chain, but it’s supposed to have a true bypass. My preamp at the time had a tape/eq loop. 

I have the loki max and it works excellently. I love it.  Easily will work as a loudness control to increase the bass and treble.   3 presets, balanced and a remote.

With regards to your your other post... I listen at low volumes a lot.  My Zu Definitions IV are very dynamic at low volume.  They wake right up with no need to turn up the volume to hear the extreme frequencies.   Two 10" dual concentric cones with no crossover driven directly from the amp.  Powered sub helps with the low freqs at low volume.  Also, you don't need a low powered amp for these efficient speakers as I am currently using a high powered SS Levenson amp to successfully drive them.

I also have the Loki max and would not b without it. IMO it is much better than a loudness circuit. I have several amps and my Accuphase amp has loudness circuit. The loudness curve sounds terrible to me. In  my situation I need less bass since my speakers are closer to the rear wall than I would like. The Loki fixes it perfectly. 

I, too, have the Loki Max, and it will definitely do what you seem to be looking for.  It's an amazing product, from my perspective.