I'll be posting here at some point when mine arrive great thread. I hope these get some exposure here on Head-fi especially as hybrids are the thing to have at the moment and these offer over the ear styling vs T-Peos and Dunu.
Well the line out of the X3 and iPod classic sound very similar and I cannot note any huge difference's. Headphone out is a different story.
Cables I use pure silver, I make my own and that way don't spend mega bucks for a well built cable. SQ wise very small difference if any, slightly more sparkle over copper.
You will want to use a LOD with an iPod and normal line out cable from X3, otherwise you'll be double amping the headphone out of the iPod.
C5D to O2 you will be...