Nice write-up. Looking forward to receiving mine all the more after reading this.

Cheers mate!

Excellent review lin! These are my findings as well in all regards.Of course I haven't burned it in nearly close to 400 hours but treble is a lot less harsh than in the beginning.If they fix the bugs and make a bigger backplate this can be the best compact dap along ak120 with 1/3 of the price.

Nah, I can work with 8.5 hours, but if it's bigger then it would become a DX100. I wished the DX90 was its size with 15 hours of battery life. Well one can wish right

Great review, agree with your assessment and it is quite an upgrade as you indicated, if would wait to funnel the funds for buying the DX90. They have done an amazing job in designing the amp stage around the fabulous Sabre dacs. If you crave for great SQ, the DX90 is it.

I truly like your review presentation, quite polished.

Thanks for this excellent review. Like the DX90 itself it is strong in the details + nice pictures!
I ordered it 2 days ago & the DN-2000's are also on my shortlist. Nice to read they have good synergy with the DX90...

Very well written review with a lot of thought going into what you have put down in words, and I would add, a fine read. 

The dx90 is indeed a huge improvement over the dx50. However I find that when using the LO to the uha-6s mkii (ada4627), and UERMs, it becomes borderline too bright. I have no problems with the gungnir at all but the transparency of the uha-6s and uerms really reveals the true nature of the sabre treble in the dx90. The dx90's amp section does a good job in hiding the sabre glare though, so I prefer to use the dx90 unamped. 

Good review!  It reassures me, as I walked into the store intending to buy the X5.  Listened to both, took a break to think about it, and then went back to buy the DX90.  I hate doing a last minute change of mind, after having already decided.  But I guess that is not so strange, to change your mind after actually listening.  Any decision made before is all based on other people's opinions.

thanks for the epic review, i am sold!! was planing to go X5 but now its DX90!! but not now, later when i go with Portable rig, thanks again ^^

Thanks everyone. Personally, I like a more neutral to slightly bright sound signature for a DAP, which is why I tend to prefer iBasso DAPs over similarly price Fiio ones. 
 
@Kerouac
The picture are not mine, unfortunately I am absolutely hopeless at taking photos
 
@thegunner100
I find that the line out is really quite neutral and maybe a little cool, but I definitely don't find it bright. The ES9018K2M performs very well, I'm not sure how much difference there is between that and the desktop ES9018 in a DAP. 

lin, Excellent Review. Great presentation and Spot On IMO. The sound quality that's available in this tiny package is truly remarkable, and "stunning"! I find it incredible that it can drive even my Beyerdynamic T1's with ease. No need to pair it with a separate amp. As you noted as well, my ONLY niggles with this DAP are its UI, Playlist & Search implementation (or lack thereof) and the 2 second cut-off bug. SQ is top notch, no question about that. Thanks again.

Thanks. I do wish that they would make it easier to create playlists as well. 
 
I'm not sure it can drive the T1s properly, but it does ok with my HE-500 (which are IMO harder to drive). 

What a terrific review! As far as playing with loud volumes without distortion, how would you compare the DX90 as opposed to spending the money instead on a good quality external amp to use with my current SanDisk Sansa Clip? Which would be clearer at max volume? Thank you!

Sorry for the late reply. I'm not sure what you mean by max volume, because if you use the Clip at full volume with IEMs you are destroying your ears. At higher volumes the DX90 is clearer than my Clip+ and O2. The Clip is good for what it is, nothing more though. 

I feel that it is very hard to chose between this DX90 and the FiiO X5. Ultimately, I ended up choosing the X5 because many people have said that while they both have good sound quality, FiiO's OS has far less bugs than the DX90 and also that the DX90 is too pricey. I could barely afford the X5. I just ordered mine an I am waiting its arrival.