Fiio E10 USB/DAC/Headphone amplifier, gets it's digital feed from a USB port.
Fiio E11 portable headphone amplifier.
Audio Technica ATH 500/700/900 series headphones usually do not benefit greatly from headphone amplifiers.
ATHs usually sound good with whatever they are plugged into.
Personally I would use a headphone amplifier with them or any headphone.