Sound quality issue

[Kenneth Strain]

I have a Cube hooked up to a Motu 828 firewire audio interface.  I use this
to feed sound to a 200W amp and Blue Room minipod speakers, and also listen
through a set of headphones.  When I playback music through iTunes, there is
always some distortion, no matter how much I tweak with the various levels.
When I use Audion, the distortion is gone, and the it sounds really clean.
This was happening in OS 9.2.2, and I just upgraded to 10.2.3, and the exact
same problem remains.  I prefer the interface of iTunes, but the sound of
Audion is so much better and cleaner.  Any ideas or comments?

-Ken