I think Photobucket's free account is pretty decent. 1 GB storage and 25 GB bandwidth per month. And I have images still hosted there from about five years ago. 1024x768 max resolution on pictures though.
If you aren't against using a full size computer personally I would get a Lynx AES16 or RME Hammerfall card and use digital out, unless you're getting a DAC that only has I2S input. This EA crap just screams audiofool bullshit to me.
From what I have read the Denon headphones leak quite a bit of sound.
A used Audio Technica (W10VTG?) might be what you're looking for. All of the ATs I have owned didn't leak much sound.
The only benefit I see with a NAS is some of them let you install Slimserver (if you use a Squeezebox or Transporter) on them directly since they are basically mini computers. Whereas the Drobo requires you to have it connected to a computer.