I think the 1000 and the 900 sound more different then alike. The w1000x is a bit bright but definitely not sibilant. The 900 had a strange upper midrange that was peeky, the W1000x is much smother and refined. The w1000x does well off of an unamped source, but they can handle some power and scale a bit with better amps. The W1000x is my favorite head phone with female vocals and classic rock, they have a sweet tone and are aggressive while retaining a good midrange. Just my two cents.
God damn head-fi :]
I will consider the W1000X...
The 900X really shines with classical music, instrumental and almost everything that does not have male vocals :D
i HAVE NOTICED THAT MORE OFTEN THAN NOT, IT'S THE MALE VOCALS THAT ARE SIBILANT RATHER THAN FEMALE'S, which is strange IMO.
The soundstage is excellent though and so is the instrument separation.
I find it quite magnificent, the fact that I can hear things which were missing on the HE-6 0_0. Subtle but there are some...