I don't understand the fascination of other commenters with mini-PCs, as the mini-ness was mentioned nowhere in the OP.
any used and decomissioned old office PC, any i5/i7 is way more powerful than you'll need for that setup. you get everything you need right in the box and you can cram it full with cheap RAM and hard disks. you get to repurpose something that's useless as a desktop workstation and not buy more future e-waste.
yes, the mini-PCs and the Rpis are more power efficient, but the operating costs of a $30-50 PC don't come close to the price of buying one of these mini-things, not to mention - figuring out how to run large hard disks with it.