Best portable digital music player?

After yet another break, I'm back seeking advice in the never ending pursuit of REAL HiFi mixed with changing circumstances. As this thread already exists, it makes more sense to resurrect it rather than start a new one.

Due to how bad the sound system is in my new car I am planning a system overhaul, but the one outstanding feeling is how bad head units are nowadays! After meeting some nice people on the sound quality competition circuit, my eyes have been opened to the idea of using a DAP as the main source instead. When the whole system gets replaced I'd need either USB, optical, WiFi or aptX Bluetooth streaming to connect to the processor (currently just a 3.5mm stereo jack to the standard head unit), but for now I need to get the DAP so I can start enjoying music again!

Things have moved on a lot since this thread was last updated and iriver now only release players under the Astell & Kern brand. On top of them you have FIIO, Cowon, Cayin, iBasso, Questyle and Colorfly to name a few, although most come with a laughable price tag. Does anyone have any up-to-date recommendations of DAPs to go for?

Apart from the requirements above, I manage all my music manually in folders in Windows with all tags removed so a player that views by folder mode would be ideal. I have no need for album-art, just a dedicated music only DAP. Expandable memory via microSD card is also a must for high speed file transfer.

I have used my phone up to present but I'm not overly keen on the results I've had and don't want to buy a software player for it if I could better invest that in a dedicated DAP which shouldn't have any glitches.

If you can recommend anything, that would be most appreciated but I accept that most of us have proper HiFi systems indoors instead.

Thanks in advance,

Tim

P.S. The first person to recommend Apple gets shot.