EDIT #3: if you're not so critical re measured distortion, then there are plenty of headphones that can meet the DCA Stealth in terms of frequency response, so long as you EQ them. In my experience with my various headphones, my favourite headphones are not the ones with the least distortion, even after EQ - there's a soundstage quality that is unquantifiable in measurements which brings the K702 and HD560s to the front of my preference......so it might be wise to temper the importance of measured distortion, however I've not listened to the DCA Stealth so I'm not sure what I'm missing from that point of view, just I know that measured distortion is not the most important variable.....I'd list it like this in order of importance:
1) Frequency Response after EQ
2) Inherent soundstage ability of the headphone
3) Good Channel Matching through the whole frequency range
4) Distortion measurements (with the proviso that they're not pathetically bad).
Lots to read about here, thanks! I figured there would be no shortage of open backs that can compete - for me the big seller is this performance in a closed-back. For a lot of people, myself included, open backs are rarely practical. If the Stealth is as comfortable and snug as the Aeon's, and sounds as good as it measures, I can literally sell all my other over-ears. ZMF Verite Closed seems to be what most people are comparing to the Stealth, but I've never heard it and I haven't found a try-and-buy seller (yet).