I had a look at the "... It's sound is legendary..." review linked to above. He is right about K450's sensitivity. It mocks the volume limiter that Apple puts on the iPods they sell in Europe Here is a press release about the units AKG will be selling in the U.S. I bought my K450's from here...

Isn't the ER4P an in-ear unit? The AKG K-450 is semi-sealed and over the ears. I wouldn't expect it to have as deep of bass response (or as great of isolation). The pair I bought seems to roll off below 40-50 hz and provide only some masking of outside noise. On the other hand, they are still...