I have used many headphones with the MixAmp. I do double amp with an 02. I have used DT990, HD598, SPH9500, X2, K7XX and currently AKG K553 Pro. And the 553 are very good IMO. They have excellent soundstage for a closed back headphone. And the imaging and positioning is great. Plus you get a nice amount of bass.
How would you compare k7xx and x2 for games and movies?