for classic-rock & old soul music the WM-Z is pretty hard to fault... imo the WM-Z edges both the F886/7 & ZX1 mainly down to the lush presentation (warmth) with these two genres..
Both the F886/7 & ZX1 are detail monsters and may appear to be cold & clinical in their delivery (I used to think that way)... not having either the F887 or ZX1 for a few weeks has left me with a different impression, I now think the F887 is very detailed with a nice touch of warmth if it's in the music.
If most of your music is old-school from way back when it might be a good idea to stick with the WM-Z.... sometimes too much detail ruins the feeling of the music, it's a age thing that older Head-Fi'ers may understand (I was brought up listening to valve amps).
reposted from the ZX1 thread...
I have been reliably informed that Chord will be using the following sources with the Hugo at the Bristol Show, UK (Feb 21st-23rd)... Laptop, iDevice & the ZX1...
http://www.bristolshow.co.uk/