Yes you do, there's no video hardware on AM4 motherboards and the Ryzen 7 chips are not APUs meaning there is nothing to control a display even though there are display out connectors on AM4 boards (they are for the upcoming APUs). You don't need a superpowered high end GPU if gaming isn't your thing, any video card that will fit in a PCI-EX slot and has the right outputs for you monitor will do.