I've had a Fiio X5ii for probably ten years now. Two microSD card slots, plays every format I've tried (MP3, ALAC, FLAC, WAV and probably more), plenty of power for IEMs or larger headphones. Can be used as a USB DAC if you really wanted, also has a line out / digital coax output for connection to external amplifiers and audio systems.
The battery life is starting to falter, so I'll change it out at some stage. The rear cover is held in place with screws, so no big deal.
It shows its age a little with the micro USB port as well, but I wouldn't consider it a deal breaker.
I have also heard that larger cards (like the 400 gig ones) can cause it to slow down a little when scrolling through menus. My cards are 128 gig and I have no problems. Could also depend on the class of card used, it's not something I've needed to consider yet.
Also be aware that the 3rd generation of the X5 is a touchscreen android thing, 2nd gen is similar controls to older iPods, with a similar form factor. They also made other DAPs you could look at (X1 and X3 from memory, there's an X7 as well, but that was touchscreen) but I have no experience with them.
Overall very similar features to the Surfans, but with two card slots and no Bluetooth at all, and I'm pretty certain no USB OTG.