The Beyerdynamic DT880 (32 ohm) would be excellent directly used with the computer, MP3 player etc. It will be the better choice for this purpose and it is a better all around headphone than the ATH-AD700 but it costs 3 times more!

There is a lot of snake oil with headphone amps especially when it comes to "sound quality" however the main purpose I would recommend using a headphone amp with the DT880 600 ohm version is solely for the purpose that they will do a better job at providing sufficient voltage to these headphone so you will be able to achieve loud(er) volumes and better dynamics. With the 32 ohm DT880 version a headphone amp will not be needed nor with the ATH-AD700.

I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne