Sony V6/7506 and Senheiser HD280 are both staples of the recording industry. Flat response, solid build quality, good isolation (the HD280 is phenomenal in this area). I would also add Shure 440 to the mix, although its sub-bass rolls off a little sooner than the other two (around 50-60Hz).
Fantastic, these are a lot cheaper then I would have expected, at least they are online. They do look a little on the plasticy side, although that could have just been the pictures. The Sennheisers at least should definitely be in most stores though hopefully both.
Have you had any experience with the MDR7509HD? On paper it seems to better then the 7506 which looks to be a little worse then the V6. Although that's really impossible to tell with just numbers.