How's the power consumption? Everytime I look at used server deals on ebay that seem too good to be true, the hidden cost is usually power. It's fairly normal for these systems to consume hundreds of watts idle, and $1/watt/year is a decent rule of thumb in the US (but much more in places like CA). And that’s not factoring in running the AC more if you’re in a hotter climate.

I’m looking at a NAS build myself and am leaning toward a consumer mobo and an older Intel, like maybe a 9th gen i5. 6 SATA ports is pretty standard, and three mirrored 20 TB pairs is a lot of storage for most folks. Boot drive could be a small NVME.