I'd welcome input from those who've done this before, or even just have more experience with PC hardware.
I'm no expert, but I do have some experience with maintaining my own server for ~10 years. I've used consumer PC's in the beginning then used commercial workstations (these are a pretty good choice), but unsurprisingly server hardware is best for this purpose. Out of lazyness I'm currently on a used Dell 1950 III (dirt cheap, insane CPU to price ratio) and it's doing well, although is quite power consuming. I've had a plan to buy a new Supermicro server board then fill it with used CPU and RAM. Math says it's the best value but I haven't done it yet.. so yeah.
Also I don't use shinobi anymore as it's buggy and fails to perform the most basic tasks like for ex. proper motion detection. Motion is my choice for now.