Read my post #3445 above.
I've compared the 600 Ohm to the 32 Ohm DT880 thru an M-DAC DAC/headphone amp.
Very hard to tell the difference after level matching (the 600 Ohm version takes a lot more voltage to drive it) the only difference I could hear was the 600 Ohm version had a very, very slightly smoother treble, but you would have to seriously A/B them to catch the difference. Mind you, the M-DAC is one kick butt piece of gear! The M-DAC drives the DT880s right!
If you have an amp that can't output enough voltage to drive the 600 Ohm version, like a little FiiO E17 or E07 or an iPad or just about any other battery powered head amp, then get the 32 Ohm version and sleep soundly at night!
I would buy based on price and what amp you are driving them with.
For example, my 600 Ohm 'phones work great with my La Figaro 336C tube amp which has a rather high output impedance and can output a fair amount of voltage but not a lot of current.
Edited by Chris J - 5/31/13 at 3:06pm