I emailed Acoustic Zen with the same question about the Silver Reference, and this is the response I got from David Schiavone:
"The newer version has a little less harshness in the lower tremble.Where they also differ is the new version has a fuller low-mid bass.These are the two areas where the new version excels."
"The newer version has a little less harshness in the lower tremble.Where they also differ is the new version has a fuller low-mid bass.These are the two areas where the new version excels."