The main positive related to the 600 ohm versions of these headphones IMHO is that they're easy to power for most people and not fuzzy about what you plug them in. Anyone who has a AV receiver, integrated speaker amp, CD player, or any pretty much audio gear with a headphone jack on it, can plug the 600 ohm version in and get a very good sound out of them. With 32 ohm and 250ohm its different. While they might be easier to power for portable devices and cheap dedicated headphone amps, they wont be as versatile overall and will be much more sensitive to output impedance of the headphone jack. 600 ohm version pretty much doesn't care. It sounds even better when plugged into a high output impedance amp IMHO, less stiff, more fluid and natural.
Indeed, I also might be getting a PB1 for $80, at that price... it's cheaper than an O2. even AFTER I buy the Connector cable I need for it :O Yea people say the build quality is kinda meh but hell for the money it should last me plenty long, the only issue is if it sound bad