With regards to Piano Guys, here's one of their tracks with volume balancing and soundstaging issues:
Vocal is audibly recessed in this song. Instruments easily overpower any vocal that there is. But then at 3:20, vocal is suddenly boosted to the forefront.
Youtube's compression doesn't help much, either, but the actual track that is up for purchase isn't much different. It's slightly cleaner, but not necessarily better.
I mean, I understand that piano and cello are the stars of the show here, but I'm not agreeing with the mastering here.
In fact, the artist (Alex Boye) also had the song in one of his albums, and... guess what? Not just volume but also frequency balancing is obviously different in that version. Alex Boye's version actually sounds... not half bad on a Beats headphone, but it's horrible everywhere else, whereas Piano Guys' version sounds like only something like the HD800 coupled with amp with the brightest, thinnest, and most artificially boosted soundstage can possibly sound good with it.
Tis' a shame, because some of their other performances are excellent. I couldn't hear anything wrong with those, but then some (especially the collaboration) are just bad. I'd almost have to question if any time they do a collaboration, they just defer to the artist that they happened to be collaborating with.
Edit: what does this have to do with the Z7? I figured... some recordings are just inherently like this, so if you're having soundstaging issues, it may not be the headphone.
