Indeed. You can build a power saving PC with eg a used Fujitsu D3401 board and a used Skylake or Kaby Lake CPU, or just get a used Esprimo P756/757 tower (E90+ for lower idle power) for 100 bucks or less. Those should idle at ca 15W (without spinning HDDs). And you can put in 4+ SATA HDDs, which is way more reliable than using an USB enclosure. Works great as an Ubuntu/ZFS server or with unRAID. Beats any Synology NAS in almost every metric.