When my old NetGear ReadyNAS Duo (2 bays, SPARC, 100Mb NIC) was reaching its EOL I looked into a purpose built server, a mini of some kind (NUC, etc), or a standard QNAP or Synology NAS. Eventually settled on a Synology DS 920+ (4 bays, x86_64, 1Gb NIC).

It's been rock solid and amazing value for the 2.5 years I've had it. It's running the majority of my Docker containers, Plex Media Server, a Linux VM, and a few other things. It also has its own shell/CLI, which is useful. I don't use Synology's "phone home"/remote access stuff, but Synology Drive and Synology Photos are great - they provide the equivalents of Dropbox and Google Photos respectively, and it works across Windows, Linux, Mac, iOS, and Android (via VPN when outside the house). No regrets at all.