@bluethinker thanks for the response, surely useful. Your experience is exactly what I’m looking for. Since you own both Diablo 120 and Luxman L-590AXII, that can’t get any better. It looks like I might need to proceed with the long delayed plan of getting an alternative dynamic amp.
I still love what the Luxman 590AXII does and will keep it as it’s a fine unit. The sound delivery although slightly warm is highly refined with a delicate touch, and as what you have aptly mentioned it will shine with other speakers. I may not have the plan for new speakers but I would still keep the Luxman. Apart from the 590AXII I also own the Naim 282/250DR separates and the latter produced a slightly more punchy and dynamic sound but lost in areas of refinement. Music sounded rough and smeared with slightly reduced clarity and refinement with the Naim on my Marten speakers. I appreciate the qualities of the Luxman after doing extensive comparison between the Naim and Luxman.
Back to the Gryphon, one of the concerns I have is on the dark treble of the 120 relative to the 300 mentioned several times everywhere. How does the treble of the 120 compare to the 590AXII? Eventually I might need to consider the 300 although it’s bulkier, heavier and more expensive.