I think 113dB would be sufficient for most people, absolutely for certain in terms of my own usage and by a large amount with lots of headroom to spare. I suppose on a practical level though I'd recommend people try their existing headphone amp with the DCA Stealth first to see if gets loud enough - then if it doesn't they can buy one with more power. Those that don't have a headphone amp and are gonna buy one together with their DCA Stealth then it's probably better to err on the side of caution and go a bit overkill on the headphone amp to ensure they're buying one with enough juice.That's correct. But you didn't account for the dynamic of music and the potential of people wanting more loudness and eq. It's kinda the same situation as EX5. If someone specified driving Stealth, I wouldn't recommend it. But something that would do 3W+ into 23ohm load. In power itself it's more easy to drive than HE6. But it's very current hungry. You just normally don't see stuff that requires this much current. And you certainly don't want your amp to run very close to its current limited and especially which of it being the silicon chip itself.
That being said, if one commits using Atom and Stealth, and knowing he wouldn't use EQ or listen to highly dynamic music or simply doesn't listen very loud, it can work.