Im not sure how much both headphones are currently retailing in your area, but when I was in Japan 1 week back, the W1000X is around 1.5x~2x the price of the A900XLTD
Take my impressions with a pinch of salt, cause i auditioned them both in a noisy departmental store and using whatever music that was played through the common cd player
Treble: Both W1000X and A900XLTD, have very smooth treble, although the W1000X sounds alittle more refined, however, this little difference is still pretty easy to pick out. Didnt hear any distortion or sibilance with both. Compared both with W5000 as well, and I gotta say i pretty much prefer the A900XLTD treble over the W5000, which was sibilant and the 'sss' sound is very prominent. W1000X>A900XLTD>W5000
Mids: Hard to point out who comes out tops. W1000X just sounds alittle sweeter than A900XLTD. My jaws dropped when i listened to this jap vocal song through the w1000x and almost got the same reaction when i put on the A900XLTD. Both are clear, detailed and lush-sounding. A draw in my books
Bass: W1000X have quite a fair bit of mid-bass as compared to A900XLTD, which appears much more tame in the bass region. Bass is not a strong point in both headphones, but i prefer W1000X, for slightly more quantity of bass, which i felt makes it more viable or versatile for pop songs. Of course, both aren't really that fast or tight either. W1000X>A900XLTD
If your looking for limited edition stuff, no doubt, the A900XLTD is a great choice, plus the wine red cups are sexy as hell
W1000X is a step up from A900XLTD, but the difference isn't that big between both. W1000X just sounds more refined at both ends of the frequency spectrum, mids are a tie though
In the end, i bought the W1000X, where i pretty much prefer the woody aesthetics as compared to the wine red cups and also the sound signature of it
I would say, head down to your nearest store and audition them both, they are more similar than different