If you prepare you media in a format that all devices can use, such as MP4 container, using H.264 video with a stereo AAC audio track then you won't need a powerful server normally because all Emby apps can use that format directly. The hardware requirements for the server will depend on a number of factors including the format of your prepared media, the type of client devices used as well as how much bandwidth is available between the client and the server.
