My gosh have the months passed. I remember having these, and I STILL DO! Hahaha
In the beginning, the A900X sounded like the Siberia V2's without burn in and a decent source. However as time passed, I noticed there was a lot more detail in the A900X, instruments started pushing away from each other and became wide with a 3d enclosed soundstage.
The Siberia V2's actually have a narrower soundstage, just by a tad bit. It's odd because they're advertised as gaming headphones...
I'm listenning to these right now, particularly Vocaloids and Nightcore which are of terrible remixed qualities with sibilant vocals. It's easy to get used to of the Siberia's sound signature after 10 minutes of listenning. It's just an easy listen, it's not laid back like the open sennheiser's, but they're not detailed so they make all recordings sound relaxing to listen to.
The Siberia V2's are what got me into the suspension type headphones, as you can see I own the Q701's and A900X's that have suspension headbands. They're just so much more comfortable than regular headbands in my opinion, plus I can hook them on my headphone rack without worrying about leaving a dent in the headphone pads :)