The AD2000X is a decent headphone in it's own right, but as you can see they're already up for sale. For my tastes, I prefer the smoother, spacious, and more well balanced sound of the K702 65th. The AD2000X has a little airier treble and much more forward upper mids, to the point where it becomes a little fatiguing for me after listening for longer.
The upper mid coloration I know is apart of the AT house sound but it seems less apparent in my A900X closed headphone. With the AD2000X it seems to border on slightly nasally when compared back to back with the 65th. But I also find the 65th to have a very natural vocal presentation.
Also, since the drivers are much closer to the ears everything just sounds more compressed and congested than the K702 65th. Now to be fair the AD2000X still has the edge in "snap and pop" for stuff like percussion and snare drums but I find the K702 65th to just be more balanced overall. The only music where I outright preferred the AD2000X is heavy rock and metal, they're good to really jam out with. Problem is, there is plenty of cheaper headphone that are sufficient for "Jamming out" so to speak.
So now, I'm trying to sell to raise funds to buy an HD-800. I did enjoy the HE-6 when I owned it but I'm leaning toward more comfortable headphones now and I'm a soundstage/space addict so I figure the HD-800's at least deserve to be tried in home for a bit.