I just got a pair of Dunu DN-1000s, and despite the fit issues -- I had to try a dozen different tips -- I'm getting some really good sound from it. However, used with Poweramp on my Moto X 32gb, they're pointing up the limitations of the on-board amp section. Or at least I think they are. I'm sorry for the length of this post, but I hope detail now will mean you have to ask for less information later.
Comparing the Moto X to an old Sansa Fuze (not Rockboxed; uninstalling Rockbox somehow screwed the on-board storage so that nothing can now be written to it, not even to reinstall Rockbox), the Moto X lacks bass weight, a consequence of this phone's known low-end roll-off. This is partly correctable through EQ, but's it's a bit of a problem for a basshead who bought the DN-1000 primarily because of its bass weight (and value). The Sansa provides a livelier sound generally, too, with thicker note presentation, but the Moto X actually seems to better it in terms of staging; there's a good deal more separation between instruments; which I think goes along with the the thinner notes. I've done some A/Bing with FLAC files (Radiohead, jazz, Pinback) and my feeling is that while the Sansa is perhaps more musical, the Moto X is actually truer to source. I do, however, acknowledge that I'm not the most experienced listener, and what I'm experiencing as separation and detail in the mids and highs could just be an underdriven IEM sounding thin.
As it happens, I have several amps: a Fiio E6, a very clean biosciencegeek cMoy that shames my earlier JDSLabs BB cMoy, and a Meier Headsix. Now, the Moto X, with its curved back, doesn't make for a great ampable phone because it won't stack well.
-The E6, of course, doesn't require stacking, but honestly seemed to make little difference over the Moto X's internal amp unless I turned the bass boost on, and that interferes a bit with the Moto's presentation.
-The Meier, with its slightly convex case is just about unusuable with the Moto. But it matches the size of the Fuze beautifully. This would make a nice little stack.
-The cMoy, too, works well physically with the Fuze, but not so much with the Moto. Its quality is obviously less than the Headsix, but it's perhaps a better option for travel, as losing it to a silly TSA agent would hurt a lot less. (I've had TSA issues before; see my earliest posts here.)
The Sansa and an amp makes for a highly portable - if heavy, in the case of the Headsix - stack, but stacking is a PitA on the road or when walking around near home. And I would miss the Android/Poweramp (or MediaMonkey, after it leaves beta) interface a ton. Despite its lovely click wheel, the Sansa is relatively crude in operation compared to an Android player, and I suspect that its DAC is inferior to the Moto's (i.e., I think the DAC is responsible for the Moto's better imaging). But since the Moto doesn't play nice with amps, maybe I should be buying a new source entirely. I'd still be carrying two devices on the road, but I'd only have to use one at a time.
So what do you guys think would be my best option? One of my amps and the Sansa? A different amp and the phone? A Fiio X5 (the X3 UI looks too gnarly for me)? An iBasso DX50 or DX90? Even a Pono player? One of the various Cowons (how does anyone keep the models straight?!)? A Colorfly or Hisound Nova? A Sony FW880-series Walkman, with its Android OS is awfully attractive, but I can't find an output impedance or power rating, so I'm not sure it'll drive my Dunus well.
FYI, 24-bit sound would be fine, but is not a priority for me; I don't own any HD material at this point. It's 16/44.1 FLACS all the way for me right now. A USB DAC is also not a priority, as my desktop has quite a good sound card, and I don't source music out of other PCs. Apple products are more or less a no-go, as I'm an iTunes hater and could never even stand my iTouch 3g; I have no iTunes buy-in at all at this point. I guess you'd say my priority is sound, but I'm not willing to deal with a really bad UI or a really heavy device in order to reap small improvements in sound. I'd appreciate any guidance you guys could offer.