Hi Scubadude, Beyerdynamic created much confusion re model descriptions. Yes the description says Premium Stereo Headphone but the model number is just plain DT990 as opposed to DT990Pro so people started using Premium to differentiate between the two. This was changed to DT990E and DT990Pro a while ago and the premium description dropped by beyer but not it seems by everyone else.
You are correct that 250 Ohm Pro and E versions sound identical, differences are cosmetic and the clamping force on the headband.