Thought I'd make and share some comparisons between the standard Opus 1, Opus 1 metal edition and the Cayin N5ii here. Can't find any reviews of the metal Opus anywhere nor any comparisons of it to the Standard opus >:[
I volume matched the N5ii and the Metal Opus with a 1khz test tone by ear to the best of my abilities prior to a/b-ing the two.
The first thing that stood out was the different bass presentation of the 2. The N5ii offered a deeper, tighter and more impactful bass. Where the Opus had more midbass the N5ii had more sub-bass rumble. Better extension on the N5ii perhaps?
The N5ii was clearer and more articulate sounding whereas the Opus had a softer impact. The N5ii was also better textured which lent a more natural timbre to the sound.
The N5ii has a bit better layering and instrument separation with more air around each instrument due to the clearer and more articulate sound. In terms of soundstage I'd say they both have similar depth but the N5ii is slightly wider and more holographic.
Micro detail wise they are very close with the N5ii slightly edging out the Opus. Again, very close and unnoticeable without a/b-ing.
Overall I'd say that the N5ii has a close to reference-neutral sound while the Opus 1 Metal has a slight warm tilt.
Now for the standard opus, I tried it out at a local audio store when looking for a good multifunctional player (got the N5ii in the end). Comparing the standard opus and the two, the standard opus has a thinner sound. This led to me thinking the N5ii and the standard opus were on par on clarity but after more extensive listening it became apparent that the N5ii and metal Opus had superior instrument separation. The standard opus sounded as articulate as the N5ii but lacked the texture and natural timbre due to the thinner sound.
Soundstage wise I found the standard opus to be as wide as the N5ii but it lacks depth and sounds 2d compared to the other 2 players. Everything else is similar to the metal Opus.
Another thing about the screens. The screen on the Opus can go much brighter compared to the N5ii so it's better under direct sunlight. However, I found that the N5ii has better viewing angles. Album art is also rendered better on the N5ii with superior Anti-aliasing and scaling.
Hope this helps