More listening and some more observations...
Hopefully this will change with the O2/ODAC, but soundstage isn't as expansive as I thought it would be. They sound very forward whereas my Pro 900 and Proline 2500 give some more space in the soundstage. Perhaps this is because midrange is more forward?
Still, detail is strong with these. Particularly in the midrange, I'm hearing more subtle sounds in my tracks than I'm used to.
Still at this point, I think I have a slight preference for my Pro 900. It's just a more intense sound, more V than U shaped. Some people dislike the "harsh" highs on the Pro 900, but I never really found them to be harsh. I can understand where someone that wants a smoother sound might prefer the SIG DJ, though. SIG DJ is just more rounded off in the highs, but it isn't quite as exciting a presentation for me as the highs on the Pro 900. Please keep in mind my music is 95% EDM, so lows and highs are of greatest importance.
Also, I find the Pro series Velour pads to be more comfortable than these. Comfort is still good here, but the velour pads get my pick.
So, it's looking like Pro 900 might still be the keeper here. Again, will know more when I test with the O2/ODAC tomorrow.
*No doubt, it's a very solid and excellent sounding headphone, but at 2x the price of my Pro 900, I'm not sure it's worth it to me. The two are similar, (you can tell they are both the "ultrasone sound") just that DJ has a less recessed midrange and smoother highs, and Pro 900 has a more recessed midrange and sharper highs. Vocals come out stronger on the SIG DJ. They both handle bass very well.
I had the Sig DJ for about a week and honestly I too preferred the Pro900 to it. Maybe if I owned it and listened to it for much longer my opinion would change but my opinion, if I don't prefer it right off the bat what's the point of "getting used to the sound". And to me the comfort was not near as good as the Pro900.
Remember, DJ fans, just my opinion. I liked the DJ, thought it was a great portable but...............