For the money you’ll spend on drives, you may be able to pay for a year of space at somewhere like www.storj.io, and use something like Duplicati to backup to them.
Because even with a shiny new NAS, you’ll still need backup for it when it crashes, something is accidentally deleted, a drive hiccups and loses data, etc.
If you already have some stuff sitting around, spin up an UnRAID/TrueNAS, but still have a backup solution.