I just love the Leben sound.  It makes music.  Really, get this little wonderful integrated and obsess on something else, because the 300 XS makes music.  Can't imagine wanting anything else for an amp.  EL-84's work great for headphones given their detail and tight base.  The soundstage is wide where it should be wide, and tight where it should be tight.  
 
My musical tastes are all over-the-map.  However, when I listen to Jazz Trio or Female Vocal the Leben is spot on.  It has the speed to play House Music and Rock out.  

OK, it cost more than the others, but you can save a fortune because you won't be swapping out amps every 60 days.  Spend the $$$ on DACs, right?
 
Cheers,
bret