I use Sony MDR-V6 headphones with the nano, and they sound great. These are the same as Sony Pro MDR-7506 (although often the MDR-V6 can be found for less money). These are actually great headphones for sound from nearly any gear (especially at the price), and they provide good isolation.
I don't know how the V-700 headphones work, but I'd stay away from them under the fear that they would be similar to the V-600s which are awful.
You will look ridiculous walking around in MDR-V6 cans unless you are in a recording studio. I hide in my office or at home with them and walk around with either buds (which unfortunately don't work with my ear shape very well - no bass) or Koss Sporta Pro (muddy and too much bass, but somehow musical and adequate for the task if exercising or walking about with ambient noise, plus you can set them around your neck when you aren't using them so they don't take pocket/bag space.)