LaughMoreDaily
Headphoneus Supremus
I haven't used either the X3 or Fiio so couldn't definitively say, there's nothing exceptional about the S5 other than value though, as you say it can be had considerably cheaper than the X2 and much less than X3 or Fiio players and the bundled phones are nice. It's not going to win any awards for sound or UI but likewise it won't disappoint for the money either.
I bought it cause I can't afford a Shanling.