From what I understand that the user did do quite a bit of tests regarding the Snapdragon version. I remember one user describing it as bloated and a bunch of other negative things. However, I do not agree with such take as I enjoy the Note 4 more so than I did with the iPhone 5s. That being said, I am debating on spending another chunk of my money on a dedicated DAP and being done with the mess that is smartphone audio quality. Seeing as I hate to have more wires than I need to, I definitely don't want to connect an external DAC or AMP to my phone.
Coming in late on this thread, I am novice and a Note 4 fanboy.
With that said, I have two external headphone amps..they are listed in my sig. Also, as you know, the Note 4 supports aptx, and I make sure any headphones I have support aptx.. With that said, I be pushing flac files through my Note 4, with a 128gb sd card. My gym headphones are my Harman Kardon BTs, because they clamp well. My main headphones are my Sony MDR 1RBT MK2. And let me tell you, not using the amps, going bluetooth, and playing flac files off my Note 4, the sound coming out my Sony Mk2 is awesome. Sure, the SQ jumps up more when wired and into one of the amps, but IMO, I really don't need the amps. So, my portable amp is just around for bragging rights, and when I am home I used the 02..
To sum up, IMO, one just needs a Note 4, flac files, apt x supporting headphones, and IMO, they be on a roll.