+1 for Audio Technica. I challenge you to find a more comfortable headphone for under $400 USD than the AD900s. You forget they are on your head other than the fact music is blasting in your ears. And their sound, personally, never fatigues my ears. I can and have listened to them for a full 8 hours while doing work, many times.
And they definitely don't need an Amp to sound great. But just cause they don't need doesn't mean they won't sound INCREDIBLE with a good DAC and Amp. AD900 has been my trustworthy cans for 3 years now, gaming, movies, and music. My musical collection ranges from Clapton Blues, George Winston solo Piano, Crystal Method Trance, to Seven Dust/Godsmack metal. And I love all my music through these babies.
But I have decided to get myself a HD650 though in about 1-2 months time, save up, as I will recable them with a DIY cable+Furutech Plug!