I've tried several different preamps in my system including the Luxman c900 which there top of the line.
I ended up with and Aric Audio Motherload XL tube in my system.
Esoteric N01 XD SE > Aric audio Motherload XL > M10X or Aric audio 300B PSET.
This feeds both my Luxman M10X and 300b PSET amps.
I have been leaning to acoustic type music in multiple genres so I was looking for the sounds like you stumbled on as well. I had a Luxman integrated with the loudness feature a few years ago and used it on low level listening. I simulate that in the Roon if listening at low levels now and want to use.
If the tubes are coloring the sound I like it.