Sorry, I don't have a S5 or Walnut.
But I do have the Wav Files Selection (all Chinese songs) that comes with Walnut ( thanks to forum member iJay ).
On my colorfly C3 combo with Hifiman RE00, those songs are just simply heavenly.
When listening the same songs from my Fiio X3 or Shanling M3, the magic is just not there.
But then again, when I listen to certain other songs or genres, the same combo of C3 and RE00 would sound meh.
So I have come to learn that synergy (between dap and iems ) and the type of genres affect how a person like or dislike the gears.
Also, everyone has different ears and listening likes.
To sum up, C3 sound is still relevant and can compare well against current crops of music players.
It's very basic User Interface and features, however, could be years behind (you can find out all these from reviews all over).
Personally, I like C3 for the sound, the small form factor, the light weight, the long battery life and most importantly, it is price cheaply at only $50~.