Upgrade path for existing freenas plex server

I recently purchased 10 of the 12TB WD easystores to replace 10 4TB WD Reds. I’m using Freenas as a Plex server. Here is a parts breakdown.

Supermicro X10SL7-F
Intel Xeon E3-1231
32GB ECC Ram
SeaSonic Plat 400w PSU
Fractal Design Node 804 Case.

I have the drives shucked, but I’m wondering if I should just add the other 10 drives as a second vpool, if so, what parts would I need to streamline the process? This was my first NAS build, and has ran flawlessly for the last three years.

Any suggestions for a new case?