Interesting to read your thoughts. I've been blown away by the GH4, as the best in all respects (most satisfying, but also the greatest "sweet-spot" performer) of the smaller Grados. With high-end Schiit gear (GungnirMB, Mjolnir2), the soudstaging on the GH4 is good. Limited, but good, and perhaps enhanced by the sheer presence, punch, and, for me, superior tonal balance compared to the others.
I must say....the GS3000e offers some of the best soundstaging in terms of overall space and separation, as well as easily allowing individual voices to stand out while still being part of a dimensional, textural mass of music, of any of the excellent components I've owned. Far, far beyond what the GS1000 and the PS2000e can do....the PS2000e is precise and present, but there is an organic, window-on-the-performance-space, yet viscerally present, quality. As someone who spent decades with excellent speakers and source material/equipment, I'm used to good reproduction of musical environments. These are the first cans I can compulsively listen to with the sense of being lost in the event. The GH4 compensates by just nailing the music. My two favorite models.
