Not sure I would ever classify the Luxman sound as “sterile”. I have never heard anyone ever describe it that way. I currently own a bunch of current Luxman models, and I have always found the tonality to very neutral, accurate and ever so slightly on the warm, but very inviting side. My Luxman gear always has me enjoying the music as opposed to analyzing sound and performance. It’s great gear and is great value. I have recommended the L-590AXII to many people and they have been extremely happy with their purchase.
Luxman tonality
I’ve seen many members describing the Luxman 509x and the m duo as warm thus colored. I’ve had these units and have never thought of them as bright or dark(warm). They are superbly neutral to me neither adding or subtracting. I find them to be very musical. A prospective buyer might pass on Luxman thinking that they won’t match up with many speakers. Of course they will. Neutral is neutral. It’s what we should want.