Closed and sealed are not the same thing - something like the D7000 are closed, but not sealed. So they leak. Based on IF measurements, the D7100 should be more sealed, but I don't know this for certain. Realize that just because they're letting sound "in" doesn't mean they're putting sound "out" as heavily - I'm thinking you're listening to music at pretty ridiculous levels if you've got the Denon models leaking enough to hear from across a room or similar.
Other models to consider beyond what Morbid suggested include the STAX SR-4070, Beyerdynamic T70 or T5p, Koss ESP/10, etc. There aren't a lot of truly sealed/high-isolation headphones, and they will not generally match 1:1 what you can get from a good open headphone. It's a trade-off.
Oh, another thought, and I know this isn't really "Summit-Fi" would be ANC headphones - like the Parrot Zik or (*ducks*) Bose QC15. No the sound quality will not compete with $500-$1000+ open-back audiophile headphones, but they isolate and seal better than most other headphones made. Just a thought, although I'm guessing you don't need this much isolation/etc to make the compromise on sound quality.
STAX SR-4070 does leak and does not isolate that much from my experience.
I have the ATH-W10VTG, same issue.
I have also a Thunderpants made by smeggy. Best isolation\leakage I have run into.
Ultrasone Edition may also fit your requirements (never tested for myself).