I'll try to explain what I'm hearing... Regarding the bass boost, to me, it seems deeper and more impactful than my F807 for sure. But it's more present in the lowest extension, not the mid-bass area, so it's not interfering with the mids in the least. With the midrange, I hear it as nicely present and not recessed at all. If anything, vocals have a more natural tone to them than the older F. I think what's going on is that with good recordings there's more space around the mids in the rest of the range, so you get this sense that things are more 'spread out' around it, maybe?? By contrast, the F807 has a more constrained sense of space so the bass, mids, and treble are sort of tighter together. The mids on the ZX1 aren't further away from the listener, I don't think, at all. Treble also has a touch more clarity and definition... again here there is more space around the notes (triangles, cymbals, etc) which gives that tactile sense of blackness between them. Here there's no false boost either, it's natural and in line with the rest of the range.
that pretty much nails my thoughts regarding the WM-Z (except the bass(?)... the more closed in sound is probably what I'm missing with 60/70's music, nice piece btw.