I also have a pair of these, and I can validate that. The sub-bass is absolutely sublime. For those complaining, the build quality really is a notch above that of a lot of headphones out there.
maybe my ears are terrible, but it is hard for me to determine any real significant change in sound between these and the Z7's. The difference that I do hear is in the depth of the soundstage and detail. The Z7 has quite wide soundstage for a closed headphone, but these do something many closed cans can't do well... large soundstage and detail/imaging,