I'm only just gtting into headphone monitoring but a friend of mine had a wonderful souding setup which was
macbook(optical)>beresford(DACing)>Xcan2(withmods) >SeinhuserHG650s
-It was really sweet and open, bass was defined but controlled, treble calm and clear and mid range had a lot of 'texture; however those things were ugly!
I'd reccomend the beresford DAC, its got an OK headphone amp on it which you can upgrade when you feel the time is right. The DAC is pretty cheap considering that it sounds really very nice (though it take a while to burn-in). My instinct is to spend the money on the cans instead of compromising and buying a headphone amp as well.
my headphone rig is
imac(usb)>mbox>sony consumer cans
-urrgh

-I'm getting a pair of Beyerdynamic dt250-80s when i can afford them/
and monitours
imac(usb)>mbox2(DACing)>azurg540r>kef coda's
-which sounds OK I guess
imac(optical)>azur540r>kef codas
-which I really like the sound of, the whole system seems to work nicely and have a nice character, nice for 5.1 Bjork
That's interesting what you say about VLC sounding better, could it be software upsampling? Does anyone know a upsampling plugin for itunes?