So... I'm back with fresh new impressions of the Luxman DA-07x. I compared it with the dac from my Accuphase DP550 SACD player using the USB input on both, the same cables and associated equipment.
The Luxman is what I would call a trusty, dependable performer. Extension is good at both ends of the spectrum, detail is good, soundstage is wide and airy, nothing is offensive. There is a really good separation of instruments and the midrange may be a bit laid back, making for a smooth, spacious, refined and relaxed listening experience.
By comparison, my Accuphase stand out as more upfront sounding, not in an aggresive or piercing, upper-mids forward way but in a midbass, lower mids and mid-mids (so to speak) -forward way. The sound is both more congested with narrower and shallower soundstage (bad) and more dense, rich, saturated, colorful and organic (good). If the Luxman is more laidback in the lower mids, the Accuphase is more restrained in the upper mids or perhaps lower highs (the piano and in general all the instruments sound warmer). There is more body to the sound of various instruments and more of a sense that the musicians are here in the room, but a bit less detail or perhaps it's just that everything is better separated with the Luxman. Treble is very good on both dacs, I'm not sure I remember this correctly, perhaps there was a bit more sparkle on high-pitched bells with the Accuphase? Again, maybe a bit less refined but more "alive".
Overall, I enjoyed a bit more my Accuphase, it's more involving and, while not quite at Luxman's level in technicalities, it's not too far behind either. Depending on the system and user preferences, I can easily see Luxman as a very good choice though. It's a very good dac and gained my respect but not quite my love.
On the other hand, I have heard a few years ago a good sounding system with an Accuphase player used as a dac, I don't remember the model. After a while, the AAccuphase has been replaced by the Luxman D10X player, again used mainly as a dac. The improvement was substantial, the sound got significantly more open, more extended upwards and more detailed, perhaps also more dynamic but I'm not really sure about that. Unfortunately the Luxman DA-10X dac doesn't (yet?) exist, perhaps that would have been a different story.