Not trolling, just respectfully disagreeing too.
Look, I find the O2 to be completely transparent and neutral. If I use a warm digital filter, I hear a warm sound. If I use a bright digital filter, I would hear exactly a bright sound. And you don't lose any details, whether it's bass, mids or treble. Simply amazing for the price. As I've said before, I've yet to find something better at transparency and neutrality, regardless of price.
So when you say you find the O2 bright on some of your HPs, I think that's because your HPs are bright. So O2 isn't to blame as it's just amplifying, not coloring or tweaking anything.
Headroom? You'll be having around 5Vrms of headroom. That isn't enough? Man, don't believe in the power is better argument. Once power is enough, and with enough headroom, extra power is useless.
I've compared the Soloist with the iFi nano iDSD, and the latter is CLEARLY better on all fronts, except the power of course. Bass, mids and treble are all better. I used the same HP, same player, same cable, same recordings. You clearly lose details on the Soloist vis-a-vis the iFi nano iDSD. I was really frustrated with the Soloist as it costs a lot more. And I honestly wanted to like it.