If building your own isn't acceptable, I like the Sony Walkman series quite a bit. I have a WM1A and a ZX300 and I have minimal complaints other than they cost way too much. There are also a bunch of Chinese brands making players with decent DAC's, but they all use the same Android interface with minimal tweaks for the most part, the battery life and UX sucks.. Definitely wish there were more high quality off the shelf players for the non-audiophile who doesn't want to use their phone for everything.
Apple iPod! By far. There are some outright strange things about the Sony app like not being able to manage a queue of songs easily without creating an adhoc playlist, the navigation is sometimes frustrating, and the default desktop app they provide to sync songs to the player in a manner that will keep lyrics and song art intact is absolutely atrocious. But pretty much everything else is good and there's nothing else on the market so...
