I’ve run a Royal N on my Schröder Reference for the last couple of years and recently switched back to a Proteus. The SPU has a softer rendition of the leading edge, music swings rather than rocks, though the results were very enjoyable even with Metallica, it’s just a bit less pacy. Music has a strong body to the sound that make up for it and gives piano the right sort of heft to be convincing and if you can align the stylus well the soundstage is huge with symphonic works. The Doors were magical too.
I did find static a bit more of an issue with the SPU a 3g than with the Proteus at 1.8.