I received my X00s yesterday and both Grimes and CHVRCHES were among my first listens. I was very pleased.
I used to have the TH900s and they were impressive, but for me, there was a little too much bass and they were also a little too intense in the upper female vocal range (Grimes, Joanna Newsom, etc.) - even with Moon Audio cables matched in part to counteract this . So far, the X00s seem to have 95% of the TH900's positive attributes, without the abrasiveness/fatigue that I experienced. I will say, however, that I found the TH900s earcup to be more comfortable, as the opening of the X00s is a little small. The X00s are quite tolerable, however, and as I imagine the X00s earcups are partially responsible for the sound, I will keep them.
I also briefly owned HD650s, of which I had no complaints. In fact, they were very good, but at the time, I was also demoing LCD-XCs, LCD Xs, and LCD-3s, all of which I preferred sound-wise (though not comfort-wise).
Ultimately, the LCD-3s ended up my favorite of any headphones I've ever listened to, but I couldn't justify the cost at the time. The XCs were a close second (and even on top at times), but the weight was an issue. The TH900s were amazing with some types of music, but almost unlistenable with others. If I had the funds, I would love a pair, but I would rather have X00s, HD600s or HD650s if I could only have one. The 650s were good, but in the end, I decided to dump them all and go with the X00, with a plan of eventually adding an HD600 and a planar (most likely Audeze, but I have not heard HiFiman planars yet).
Obviously, with headphones YMMV, but long story short, I like the X00s with female vocals, especially those backed with fun synth arrangements, such as Grimes and CHVRCHES. They also did well with another favorite test track of mine, The Doors' "Riders on the Storm." I will give them the "Joanna Newsom squeal test" (which I just made up, and mean no offense to the awesome Joanna or her hilarious husband) tonight. I'll probably try some more analog indie rock, classical, bluegrass, and other genres, as well.