i just wnt to sleep, and this thread gone in a very bad way...
First, dude with streaming, don't buy x5 or x7, you are clearly not enough happy with it.... Second, Fiio has already build something, just for you. It is a DAC/Amp that you can connect to [i don't know if it has to be android] devices. Fiio e18. It will not take any of your devie away, and add a nice DAC, and a nice amp. Now, you can get that device and add it to your phone or other devices, and keep a nice battery life, and everything you already love. You are at fault for missing the right thing you needed. I don't have access to free wifi, not even 1% of the day, and internet taxes, being it 3g or 4g or whatever are too high to even consider. I hate streaming, tried it, i have narrow tastes. But audiophiles are rich people usually, and 700$ price point is a competition to ak240, cowon p1, etc. You don't understand that being an audiophile is itself a hobby, collecting music, labeling it, mp3tag, searching for music, transferring it, listening to it in perfect conditions. no offense mate, but you can consider other options besides having a DAP.
I need a 5tb drive to keep my music and anime collection with me. 3tb was not enough. If i will ever go streaming, i will no longer enjoy music nor anime anymore. Just because.
no offense, the curved edges are a very very bad ideea. I have a phone with curved edges, ZTE Blade VEC 4g... It is awfull, and i installed a case that makes the eges edgy. the phone slips out of hand, loos bad and feels bad in hand without edgy edges, the buldge on the side is a pretty bad ideea as it will be a weak point.the volume can be pure buttins. ak240 design made the volume much less prone to damage, but stealing a design is not nice nor productive.
Again, i don't think that 8 hours of music will do, so fiio, please install a bigger battery... just please do this, it is a good ideea to have more battery. Also, wifi would seem nice but pointless, unless you can add a feature to add files from pc to player by wifi, something like total control of player by wifi, and even DAC function from pc to player by wifi. These seem interesting, and pushing the envelope, this is what head-fi is all about. want to push deeper, there are other things you can do , even at this price point without having to sacrifice anything. like the circuits to be able to charge without damaging the battery, while it plays, and streams wifi. Even better, i would pretty much like to be able to DAC thorught wifi, while i transfer files through wifi to microsdcards. I don;t want more microsdslots, as it will become pointless at some point, but i would love more space. SSD slot?... or anything like internal memory?... OR at least more battery?... please?..
Also, fiio, i know who your market segment are, but please consider that there are players that are thicker/bigger and are still bought because they have more battery/more space, even through they are bigger.