there lies the problem for most people judging the A-series to the WM-Z... I've owned/own both the US & Japanese versions of the WM-Z, I've also owned/own the Euro versions of the A & X-series.
UELover is right in saying that the A & X-Series are similar, they have the Sony house sound which is on the 'warm' side but detailed, some don't like that. I never liked the WM-A (lasted four days with me before being slung back at Amazon, mainly due to the pitiful volume-cap) and I only like the WM-X with certain genres ie old Soul music... the WM-Z is way more neutral sounding and I cannot hear (well remember) any discernible difference between the two versions of the WM-Z I've owned, in fact I've just bought another Z1070 (I now own two).... to my ears the WM-Z is by far the best sounding DAP I've owned, there may be better but I'm well satisfied with my purchases... if I have to be critical of the WM-Z, it is not very forgiving on poor recordings but that goes the same for any quality source (not speaking of only DAP's here).
Edited by OK-Guy - 8/16/12 at 2:02am