If you are at all interested in high resolution files, then the soon to arrive Astell & Kern AK 240 will have 256GB of internal memory, and takes 128GB microSD card to get you up to 384GB! Price is $2500, however, so it's way out of my league. But it's got everything and will probably be truly great. For lesser money (less features, formats, memory, etc.) check out their AK120 II at $1700 or AK100 II at $1000.
I've ordered a Pono player at $400 which has 64GB of internal memory and an SD slot. Unclear if its SD is limited to 64 GB or if it can handle 128.
Have you looked at iBasso? The DX90 comes in around $480 including 128GB via SD card. There's no internal memory -- everything gets stored on the SD cards, but of course you could have many cards for different subcollections of your music library. There have been some criticisms of the software but because of its affordability this is what I'd been looking prior to Pono.
All of these handle high resolution files, but if you have DSD files then so far as I know the iBasso and AK are the only portable players that support DSD.