I've been through many a music machine since my first true mp3 player (after a year of fumbling with a half-broken Sony MD player), but if I could shove a 512GB MicroSD card, new battery, and new screen into my old DAH-1500i MobiBLU Cube[1], I'd pick it up again and never let go. Even without playlists, it was perfect: tiny, but with a display (which I didn't even need to use half the time, as I could navigate its menus from my pocket, sight unseen), nicely clicky buttons, simple interface, quick startup.
So, you know, I could listen to music.
There was like a two-year period where these monochrome OLED jewels were offered (Sony's NW-E505/7[2] was another gem, horrible PC software notwithstanding), before ghastly full-color LCDs took over. And they topped out at around 4GB (32, if you include the Sansas that came later, which I don't). Damn shame.
[1]https://duckduckgo.com/?q=dah+1500i&iax=images&ia=images
[2]https://www.crutchfield.com/S-PPVgsomq9x6/p_158NWE505B/Sony-...