I tested SP1000SS against my WM1Z using my Just ear MH1 and also DITA awesome cable (copper version) in balance mode for both. To me I found the difference is so small that it is almost certainly unnoticeable in non-critical listening condition. That said with the SP1000SS being also nearly as heavy as the 1Z but the 1Z surely winning on the battery life competition and I really hate those 2.5mm jacks now, personally I'll pick the 1Z over the SP1000SS. EDIT: I also find that in general the user experience of the 1Z is superior to the SP1000SS. AK's insistence in using those tiny control buttons closely placed together is an issue for starters (the buttons on the SP1000SS is no bigger than those on my AK70 and previous 380, even though the device is MUCH larger). The volume dial which lacks a lock switch preventing it from accidental trigger is another. The dial looks good but lacks practicality, Sony's way of going with pure buttons is more utilitarian. At the summit-fi end of DAPs where SQ difference is now so tiny, to me it is much more important to look at the overall package from a user experience and software POV and that's where the differentiation comes out the most.