How much isolation is absolutely required here? If they don't gotta block a jet engine or whatever, the ATH-ESW9 would be my pick over the A900X and a lot of other closed cans (I haven't heard the new Sony or V-MODA cans (I don't think many people have...), and dislike Beyer (so I won't comment
)). If you need more isolation though, I'd probably point towards the HD 380Pro or Bose AE2 (not kidding). The AE2 might actually satisfy his desire of no boosted highs (they're kind of a dark headphone, the treble isn't jacked, and they're very easy to just listen to).
Why no A900X love? Because the headband/fit is somewhat particular, and I don't like their specific coloration. That said, if they fit you (or your friend, it sounds like) properly, for the ~$200 they go for, they are not a bad headphone at all. Best Buy (Magnolia, more specifically) should have both the A900X and ESW9 as demonstrator models, so you can test fit and get a rough idea of the sound. If they fit fine, and you can get into their sound, they would probably be a better choice than the HD380 (but the HD380 is probably more mobile given that they fold and come with a hardcase), but the odd fit should be mentioned imho ("how are the children supposed to learn how to read, if they can't fit into the building?" -> "how are the headphones supposed to sound good, if they won't stay on your head?"). I think the ESW9 sound better, fit aside, but they tend to cost more and the wood is likely more fragile than the aluminum/plastic on many other cans.
Other closed-back models I'd encourage you to consider:
- Kenwood KH-K1000 (will do everything mentioned, really really well, but they're $400+)
- Bose QC15 (only if you really really need the isolation, but they're worth mentioning just for that imho)