The FiiO E7 has a really pleasant balance and sound stage when used as a USB DAC and as a line-out amplifier, but it really adds nothing to a headphone out socket. In fact, it can be detrimental to the sound if used with headphone out sockets, so if ...Read moreyou have a line-out instead or a line-out switch I recommend using that instead, or use the USB (which is by far the best sound quality).
It was very easy to use with both my home Mac and work PC. PC was just plug in and switch on, but with my Mac I had to enable USB DAC in system preferences, then I was off!.
I'd definitely recommend this for people who spend a good amount of time listening on headphones; the real benefits are evident when you use really high quality headphones.