Review:
Build:
The X5ii body feels so much better built than DX90 and Pono, the metal body feels much hardier, in fact similar to quality of AK100ii/120ii body. The screen of X5ii is sharper and more vibrant than DX90 and Pono, but the scroll wheel is a let down, it feels cheap and flimsy compared to the body and screen, along with the dreaded way it doesn't sometimes register input at each click of the turn, only a minor issue, mainly just detracts from feeling of quality.
Sound:
The X5ii is in deed no better or worse in technical performance than DX90 or Pono, the sound that X5ii achieves is unique, the epitome of smooth yet fully detailed, in fact the musical detail from X5ii is easier to hear than DX90 and Pono, the X5ii presents everything so fleshed out and close up without a hint of congestion or sharpness, the timbre is excellent, it just lays out the detail effortlessly, compared to DX900 the X5ii is smoother, more refined, presents all details without a hint of sharpness, yet it is also more upfront than the DX90, the vocals for example have this amazing density and sound 'larger', more enveloping, It's an interesting combination that I really like. The DX90 is sharper, harder edged, better defined, but also more distant, thinner, sounds 'smaller', and quite often presents sibilance and sharpness. I do not consider the X5ii colored in sound, I find X5ii, DX90, Pono all to be neutral in response and balance, they just have different presentation characteristics. Neutral though it may be, is the sound natural? No dap sounds completely natural to me, all have shortcomings.
The X5ii's achilles heel is it has less impact throughout the entire frequency range, you can hear all the details from X5ii even better than DX90 and Pono, the vocals of X5ii are even more life like in timbre, but you simply cannot feel the impact or immediacy of anything, the vocals do not feel like a "live" performance, more like a ridiculously smooth studio recording, it looses in PRAT big time to other daps, especially so with the wrong pairing. As such I can only recommend the X5ii if you want the most fatigue free presentation available, mainly listen to music for relaxing, or mainly listen to relaxing music. or even if you just want to analyze detail the X5ii is superior, the X5ii really does sound like a piece of super smooth studio monitoring equipment. But for enjoying music energetically, the X5ii does not work out.
Conclusion:
To my ears, all these daps are resolving the exact same detail, yet presenting them in quite different ways, as such, it essentially comes down to preference of sound presentation and more importantly, the pairing of headphones making a match that in turn satisfies your preference of sound presentation. If you want toe tapping factor look at dap's other than X5ii. Most will assume that the X5ii is warm, or rolled off etc, when it is not, it is extremely detailed, neutral and balanced, presenting fleshed out detail without a sense of immediacy, utterly smooth. But lacking energy, which is extremely important to conveying the emotion in a lot of music. Music which does not rely on conveying energy will sound phenomenal out of X5ii, like some acoustic, or relaxing piano etc, the X5ii will have the Pono and DX90 beat hard with such music, but for the majority of music, the X5ii simply falls short in conveying the proper sense of energy and immediacy, which makes it hard to recommend as an all round dap.
Note: One should remember that it is impossible for anyone to write a completely subjective review, as we all have different reference points and perspectives, which influence our thoughts whether we like it or not.
