As I said, I have two MicroSD>SD adapters with 128GB SD cards plus the internal memory of 64GB = 320GB. I'm considering a 256GB SD Card that would add 128GB for a total of 448GB, but I have not tested that combo.
I currently have more high resolution music than will fit on these cards.
I'm also considering downsampling everything to half sample rate, but leaving it at 24bit.
I took a 192/24 flac album and converted it to 48/24 flac and it sounded VERY close and took up 1/4th the space. I have a ton of 96/24 flacs that I could convert to 48/24 and a bunch that are 88.2/24 that would sound fine at 44.1/24.
It would free up half of the space, and maybe get me back into what will fit internally. I don't know of a program that I can use to do this easily or I would have done it already.
One advantage to this sloppy arrangement is it makes the AK120 look like a broken POS so nobody will steal it.