If anybody's interested, here's the differences between the Pros and Premiums
The pro's have
* higher clamping force
* more bass
* coiled cord
* simple old style "retro" look
* available in 250 Ohm version only
* easily replaceable headband padding with snap buttons
* no carrying case
* cheaper (normally)
Premiums have
* lighter clamping force
* less bass, brighter, more "airy" sound
* long (3m) straight cord
* available in 32, 250, and 600 Ohm versions (the 250 has the same drivers as the Pro)
* comes with a carrying case
The pro's have
* higher clamping force * more bass * coiled cord * simple old style "retro" look * available in 250 Ohm version only * easily replaceable headband padding with snap buttons * no carrying case * cheaper (normally)
Premiums have
* lighter clamping force * less bass, brighter, more "airy" sound * long (3m) straight cord * available in 32, 250, and 600 Ohm versions (the 250 has the same drivers as the Pro) * comes with a carrying case