I currently use an old boring HP tower. Nothing fancy, I think it’s a quad core AMD APU. But if building it from scratch I would get a $35 thin client off eBay and stick a NIC in it. The CPU load is minimal as the network card does all the processing. I do have 8 TP-Link access points and a hardware controller as well as three unmanaged PoE switches for the Wi-Fi but that would be the case regardless of what my router is.