I received Pro900 yesterday and I still burning in it.
First impression Pro900. TBH, SUCKS! as the time goes by, one of the cans that IMPROVE A LOT during burn in. Now it is freaking good with electronic music and I prefer it without an amp/dac, straight to the iPad/iPhone, the sound is really great! High sometimes can be harsh (not always). Bass is solid, not boomy, just perfect. Mids kinda recessed but i do make it bright by eq. Simple eq can improve it A LOT NO KIDDING. Overall, im still burning in this at least 200 hours to get the actual sound. Yes, thats the con of Pro900, freaking long burning in time.
X2? since im a basshead, this X2 is really neutral. Listening to Celine, concert, Sia is another level. "P/s: Im fan of IU, a korean singer, her songs are about perfect with X2", listen to her songs is like having her in front of you. Pretty next level huh? Hahaha.
What else u wanna know?