You aren't going to find any audiophile-grade headphones that will be reasonably driven by the FiiO E3. Buy the Mad Dog by MrSpeakers and a Schiit Magni amp.
DivX web player is broken for me (no video and continuous error sound is the only audio), despite being fully up to date and reinstalled several times. I have tried VLC and Quicktime, but neither will play .mkv and .avi videos meant for playback by DivX (VLC will, but it crashes shortly after)...