I doubt you can call them the best sounding earphones in the world, as there are such a large number of types.
However, BBC Music Magazine reviewed earphones in their October 2006 issue, and they gave the A8s five stars and nominated them as "This month's star product." The review stated that "they do full justice to the sound coming from the headphones socket of any iPod or MP3 player." & "you may well end up thinking the high price is well worth paying."
They also lauded the ergonomics and fit of these earphones.
For pure audio reproduction with a minimum of distortion from outside sources, I would go for earphones from Etymotic, used by professional musicians during concerts to drown out extraneous noise. These have migrated to the portable MP3 crowd. I can't use them, as I don't like the sweaty feel I get from having these plugs inside my ears -- and I also wish to have a little contact with what's going on around me.
http://www.etymotic.com/