Honestly, I have the impression your setup is oversized (knowing nothing about what you want to run)

NAS systems set on idle like 90% of the time unless your are doing really crazy things with de duplication and distributed iscsi for super big volumes, that I have the impression your are not going to do.

You can probably cut the performance/specs to the half and still being good for the following 10 years and the extra that you will save on electricity too.

As a comparison I checked this built against your synology and in the multicore setup is x10 more powerful (cpu-monkey.com/…/compare_cpu-intel_celeron_j4025-…)

Just my two cents