It makes strange reading this thread, why would a cheap headphone jack on an integrated amp sound anywhere near as good as an amplifier designed for headphones :?
I've owned three different headphone amps, even my £40 cheap chinese ebay headphone tube amp sounded much better than the headphone jack on my Cyrus 8VS2.
Headphone jacks on integrated amps are generally included for convenience and they serve a purpose. But to get the best sound from headphones generally a dedicated amp is needed. Common opinion, of which I fully agree with based on my own experience, is that the Q701s need a good amp to sound their best.
My DVD player also plays CDs, but that doesn't mean it sounds as good as my dedicated CD player...