should i buy this or a fiio amp/dac?
Which headphones do you plan on using?
E17K or E18? I am assuming that at this price point you are not looking at the Q1...
The feature list of all these are easily available, so I am assuming that you are asking in terms of the sound.
The only Fiio products I have heard/owned are the E07, E17K, and X5 1st gen. Some people say that the E18 is not as good as the X5...
Most of my listening comparisons were done on a HD800 and Denon D7000.
I find the E17K sound to be too fun to be used for any kind of critical listening, it has the kind of sound that jumps out as you which at first listen might sound very engaging.
Depending on what you want to achieve, it might be "good enough". For the record, the X5 does sound "better" overall, darker background, more detail, etc...I find the signature to be very slightly on the dark side which might make it sound "uninteresting".
The XD-05 (stock), sounds about the same level as the X5. The FR is probably a little different, with a slightly brighter signature. Which one you prefer will depend on your personal preference on sound signature. The thing I like about the XD-05, is the op-amp upgrade, with the v5i it is better sounding than the X5 particularity in areas of detail and control.
Also why stop at Fiio? The Oppo HA-2 is also a very popular choice around this price