I am currently rocking a Shanling M2X which I bought secondhand for €75,- from the local classified ad websites.
Officially supports up the 512Gb but according some reviews it can do up to 2Tb microSD cards ( headfonics.com/shanling-m2x-review/ ). I currently have a music collection of about the same size. The Shanling M2X can drive all the IEMs I throw at it, has enough file system support to read just about anything and has WiFi and Bluetooth. Although the WiFi can only be used to wirelessly sync files (which can be a pro but also a con, depending on how you look at it).
However if you don’t feel like going secondhand, Shanling offers a whole bunch of devices meant for offline playback of local files.