Important features to look for in an AV receiver include power output per channel, support for surround sound formats like Dolby Atmos and DTS:X, HDMI inputs and outputs with support for the latest video and audio formats, built-in Wi-Fi or Ethernet connectivity for streaming audio and video, automatic room calibration systems for optimal sound quality, and compatibility with your existing speakers and other AV equipment. Additionally, consider features like multi-room audio support, integrated streaming services, and smartphone app control for added convenience.