Here is a portable external hard drive with built-in WiFi that lets you stream content to 8 devices. The Passport Wireless Pro comes with USB 3.0 for fast data transfers. It can also serve as a power bank for your USB devices. You get access to its data through an iOS/Android app.
With Plex, you are going to have an easier time organizing your collection. There is also a SD 3.0 card reader for media transfers. This external hard drive is compatible with Windows and Mac machines.