Based on you liking what you hear when you switch on "Loudness" you're not missing the mid range, you're missing probably a fuller bottom end and possibly some crisp highs. The Loudness button accentuates bass and highs (and as a result it actually makes the mid range less prominent to our ears). So you might want to use the digital EQ function in Roon if you use Roon, or get an EQ of some sort, add a sub, experiment with moving your speakers around etc. OR, change the speakers to Klipsch, Vu, Tekton, Volti or other models of DeVore all of which will be probably more to your liking.
Luxman leaves me wanting
My current system is a Luxman L590-AXII driving DeVore Gibbon Super Nines. My source is Lumin U1-Mini (w/Sboosterj and Denafrips Venus II. Also a Rega P3. Speaker and interconnect cables are circa late 90s Cardis Cross There is a lot that is right about the sound of my set up, but I feel it’s lacking fullness in the midrange. When I turn on the loudness on the Luxman, I get the meaty weight in the mids I’m missing, but at anything but low volume, it alters the sound in a negative way.
I had considered a tube Integrated before I got the Luxman, but liked the L590 when I heard it. Now I’m wondering if I should have gone with tubes. (At one point I had a BAT Pre w/ a Classe amp and loved the bloom in the mids and vocals). I’m attracted to the LTA 40+ from the good reviews and long tube life. I’d be interested in hearing one with my speakers, but there are no dealers, so I could buy and return if I’m not thrilled, but wanted to know anyone has heard the 40+ with Super 9s. Also interested in other options to get a richer sound. Budget is around 8k.