Well I hope other than these niggles you are enjoying the player? Do you prefer the sound over the AK100? I must admit I preferred the DX100 over even my former RWA AK100. I just didn't see the appeal for that DAP in terms of sound quality. While it was a good player it was not better than my Studio V 3rd ANV which is less than half the cost of it, has much better battery life and it much sturdier built..... Then again the Studio V 3rd ANV is a picky player in terms of finding a perfect IEM to match its sound signature & it also has it's own issues.... But once you find it oh boy! :).
Loving the SQ Lee! Glad I changed over. I must admit I found the stock AK100 quite good with the IEMs I have, especially the W4Rs. The SE535 limiteds definitely were more peaky at higher hertz. How much is their signature vs the impedance issue is guesswork. I did like the small form factor though. That said, I will probably listen to DX100 90% in quiet environments so its size isn't a bother to me especially since I don't need to lug an amp around. And Gapless is essential for me as I have many gapless albums from DSOTM to Classical. That was the main reason I decided to upgrad to the DX really. But having done that, the SQ is another level up.
The DX100 powers my headphones perfectly. And this is really important for me. My hearing is only about 70% of perfect hearing. Fortunately I am fairly flat across frequencies but do drop off a little more over 8kHz so it's mostly a volume thing. So I do have my volume up more than most people. My audiologist says there is and big variation on people's hearing and many don't even know they don't have even frequency hearing. Definitely explains why some people can rave about a particular HP while others find them less attractive sounding. It's always personal.
I don't have extremely high end headphones because I use IEMs more, but they're not bad either. I tried a set of Amperiors which were readily available retail here (I would have liked to try some HD25-1 IIs, but no one has them in my hometown) but I did not find them neutral. Too much mid-bass which some comment on and like, but I don't. Could be related to my hearing I guess. I really like the DX100 with my Shure SRH840s. These phones seem to suit my hearing really well. But, there is a shop in Melbourne that has a stack of high end HPs I can try so I'll spend a couple hours there with my DX next time I visit.