The third is a Loki Max remote EQ in my main hifi pile...this thing is brilliant.
I had a Loki Max on order when you wrote this; got it two days ago and have been fiddling with it. I agree completely with your assessment! My initial setup is to use the presets to approximate different equal loudness Fletcher-Munson curves.
The loudest I typically listen is about 80 dB SPL, but I do a lot more listening in the 65-70 dB range. With the Loki Max, I now can dial in the appropriate F-M curve to have a richer, more detailed soundstage at lower volumes.
I hadn't really thought about it before, but F-M curves lead to the logical conclusion that, if your system is truly linear at all listening volumes, you can optimize the sound for only one listening level. The others really need to be corrected using EQ based on the science of equal loudness perception.