O.k. I think I nailed the pin on the head. According to this post http://www.head-fi.org/t/608553/review-comparison-two-flagships-pass-in-the-night-sony-xba-4-review-vs-the-mdr-ex1000
that is exactly what is happening with the XBA-3. YUCK!!!!!. It sounds like crap on my nice amp!!!! The treble IS in fact horrificly audible. I can't even believe the differences. I don't know the output of the ipod touch vs. ipod classic, but I read somewhere the ipod touch is around 5-7 ohms. The classic must be a bit higher, because it goes from a fairly soft neutral sound, to a more detailed brighter sound on the classic and then to an all out metal treble fest on the duet. See this image:
That looks almost exactly liek what I would expect listening to the xba-3. The ipod touch would be the red line at <10 ohms so even lower probably. The classic is probably around 10-15 ohms? And the duet is the black line at 30 ohms. I think what kills the sound is probably that 10khz bump really bringing out the metal sounds. You can see at the red line, or lower even, that hump is more in line with the other treble better.
It's really too bad. If there was a way for me to keep the xba-3 at that red line across sources I'd be an extremely happy man... Although, I suppose I could have them as my "ipod" headphones. But then I need another $200 pair for my computer? UGH....