I have owned both Eidolons and Eidolon Diamonds. I had the Eidolons for about two years and I currently own the Diamonds for the last 18 months. I agree with you that the Eidolons are fabulous. The Eidolon Diamonds take it up a notch more. I won't digress on how great the Eidolons are, but here are my obsereved differences between the Eidolons and the Eidolon Diamonds:
Bass - Diamonds have more visceral bass and better bass extension
Treble extension - it seems that symbals have much more body and the instrument decay and 'naturalness' are far superior
Resolution - seems much more lifelike and the 'space' around instruemnts are better
Midrange purity - similar
Soundstaging - better in diamonds, but very close
depth - similar
density of images - better in diamonds, but very close
I have found that my upgrade to the Diamonds is one that I haven't regretted for a second, but like everything else in high - end audio - you have to judge the 'law of diminshing returns' for you own preferences.
Bass - Diamonds have more visceral bass and better bass extension
Treble extension - it seems that symbals have much more body and the instrument decay and 'naturalness' are far superior
Resolution - seems much more lifelike and the 'space' around instruemnts are better
Midrange purity - similar
Soundstaging - better in diamonds, but very close
depth - similar
density of images - better in diamonds, but very close
I have found that my upgrade to the Diamonds is one that I haven't regretted for a second, but like everything else in high - end audio - you have to judge the 'law of diminshing returns' for you own preferences.