I ended up with the Sony MDR-V600. Not a high-end audiophile headphone, but
it has response from 5 to 30,000 Hz and is a circumaural design that does a
very good job of blocking out room noise. It's ruggedly built and folds up
for travel. Definitely a step up from the MDR-V150 that I was using.

However, I'm going to build an inline attenuator to reduce the volume.
Right now I use the headphones with my laptop volume turned almost all the
way down, and there's hiss.