Yeah, audiophile terms are a bitch because I could mean one thing, you could understand another. With the new beta-firmware the X3 has gotten a bit crisper, slightly more details, etc. When I say 'it´s more revealing' I mean that you now can hear errors of the recording better (if it´s a bad recording). In case of well done recordings it´d be more details.
The HD-558 is balanced but tilted towards warmth; perfect for the X3.