I'm not a headphone junkie by any means as of yet. I have only tried Sennheiser HD598, Audio Technical WS99 (Bass headphone closed back), Audio Technica WS1100i (Bass headphone, semi-open), and HyperX Cloud II's. Out of these the 598's were best likely just due to being open. Competitive gaming cares more about soundstage, seperation, and good high end.
AD900X, according to Youtube, Youtube comments and other shit apparently don't sound that much different than the AD700x. Should also be a good option.