Upgrading existing NAS w/ possibly DIY NAS?

[Enquiries]

Hello, I am approaching my data limit on my existing QNAP TS-453A (running RAID 10, with 14.10 TB usable storage, all slots filled), and I am looking to expand my storage.

Current use case is holding media for my Intel NUC to MAP it in Windows and behave as a Plex Media Server.

I am considering building my own NAS and not buying a NAS, and considering building an 8-bay NAS (RAID 5).

How cost-effective and reasonable is this for my current use case? Is a DIY NAS power consumption much more than an off the shelf NAS?

[ed]

A NAS will most often be a more power-efficient solution. Also, the warranty is much simpler. And finally OS upgrades and functionality.