Skylab I guess your impressions validates impressions from people(including myself) using the speaker taps to drive them. The sound is so good from my fisher that I have no desire to try them on any other amps. As good as they sound with my fisher, I bet they are just heavenly out of the speaker taps of the leben.
Yes, it does indeed seem to be so, that there is a little bit extra to be squeezed from the HE-6 when they are given access to what for a headphone should be a ludicrous amount of power. This must also be why I always favored them from the Mini-Torri up until now.
But on the flipside, the HE-6 do sound good from many standard headphone amps. As good as they possibly can? No. But very good nonetheless. What that means is that they can be purchased and enjoyed by someone who has a reasonably powerful headphone amp, and then also provide an upgrade path for the future.