Xduoo X3 can play WAV files. Could you do a direct comparison if you haven't already?
Ok here goes after a bit of side by side listening.
Firstly to explain my priorities. I like my rock and metal foremost. Outside of this there are random other artists I love including Suzanne Vega, Tori Amos, Prince, maybe even a bit of Justin Timberlake and Beastie Boys.
I want to hear some details, I don't want to hear anything veiled or muddy, don't like harsh / tinny / sibilant sound, and I'm not into anything outlandishly bass heavy.
I also don't necessarily want something that relies on the perfect master and mix to sound good, which I often read is a feature of high end stuff, although I've never ripped a CD below MP3 320 because I want it to sound as good as it can. A big priority for me is vocals.
I want to to soak up the atmosphere of the decks creaking in Iron Maiden's 'Rime of the Ancient Mariner', to rock out to Airbourne, and to believe sincerely that Justin Timberlake is bringing sexyback. Only one of these was on my playlist for this comparison though, as I just played what I fancied listening to, which I knew well enough, and which I have already converted to WAV (and into single tracks per album using Foobar).
The songs were:
Delain - Send In The Vultures.
Justin Timberlake - Futuresex/Lovesound, Sexyback.
Suzanne Vega - Marlene on the Wall, Blood Makes Noise. (some patience required on the Walnut as these are later on the album than my other choices, and no option to skip or fast forward through)
Marillion - Assassing, Punch and Judy
Blind Guardian - Sacred
All listening was on my Asura v2.
Every track sounded great on both players, and a lot may be down to my personal preferences which is why I've detailed them. Both had nice fast punchy bass through the Asura, and plenty of detail. I couldn't detect anything lacking as such in bass, mids or highs to my ears. But each time the Walnut made me want to keep on listening, as the overall presentation wowed me and yet was never harsh or tiring. Both male and female vocals sounded stunning. I couldn't detect any specific lack of detail compared to the XDUOO as such but I'm no critical listener and YMMV. It wouldn't surprise me if an expert critical listener was to say the XDUOO had more detail, else why would the Walnut sound smoother? Soundstage through the Asura goes hands down to the Walnut in my opinion.
The difference between the two only magnified if I tried increasing the volume.
At what felt like similarly loud volumes, the XDUOO wasnt doing much for me. What had felt like details started to feel like discomfort and tiring to my ears, and I just wanted to turn it right back down again.
Turning the volume up on the Walnut had no such affect. It went from sounding nice to sounding epic.
On the basis of all the above..For me the Walnut wins hands down, and not just based on their relative price points. If I had to give away one of these players and make do without it, I'd give away the XDUOO. If I wanted to show off the lush sounds of my Asura earbuds for someone to try out, I'd plug them into the Walnut.
I love this player. Yes there are compromises. If I use the Walnut, I can't have all my music collection to hand in one place, or access a chosen song quickly anywhere on any of my albums, like I can with my other players. As I've ripped whole albums, I can't remind myself of the name of a song I like, or just go back and play that song again (unless it's track 1). But the Walnut has me thinking 'maybe if I got multiple SD cards, and something to keep them in, and created an index of what albums are on which card...', and that just wasn't supposed to happen!