Help sanity check my planned NAS

Heyo there, this is my first time touching anything server hardware related, advice is appreciated

I have an old Xeon W3550 CPU that I'd like to use in a TrueNAS Core build for my home network. I've had two of these CPUs collecting dust for many many years and want to put at least one to use, I hate the idea of throwing them away. I already have an olld GPU to use. Seems like the cost of ECC RAM+mobo+chassis+PSU+LSI HBA card will be ~$500 - the big thing I'm iffy about is that this system maxes out at 24GB of RAM.

This would just be a NAS, no VMs or funny stuff, and I don't think I care about AES-ni or deduplication. Though, I do want it to be the main storage platform for my home workstation and Plex server / game server / general archive, and so I'd like it to be very reliable.

The planned array would be 120TB raw

pool 1: 2x18TB drives, mirrored

pool 2: 6x14TB, raidz2

+ expand with another 6x14TB when the time comes?

am I being stupid? will this run poorly? is there a clear, better way to spend my money? if so, what use case do these CPUs have anymore?