The TX-NR525 provides up to a 5.2 channel speaker configuration, while the TX-NR626 and TX-NR727 have provisions for up to a 7.2 channel configuration, Dolby ProLogic IIz processing, two HDMI outputs, and Marvell QDEO up to 4K video processing and scaling.
Another connection bonus on the TX-NR626 and 727 is an MHL-compatible HDMI port, which allows direct access to 1080p video and up to 7.1 channel surround sound from compatible portable devices, such as Smartphones.
Also, in a move that bucks current connection trends in home theater receivers, the TX-NR626 and 727 each provide a dedicated phono input - so for all you vinyl record fans, this is something to consider. On the other hand, none of the receivers provide 5.1 or 7.1 channel analog audio inputs or outputs.
On the other hand, to better accommodate the increase in portable and wireless device use, all three receivers also have built-in USB ports for accessing audio content from iPod/iPhone or USB flash drives and DLNA compatible network connectivity, Internet Radio access, and direct downloading of firmware updates. The TX-NR626 and 727 also have convenient Wifi and Bluetooth capability built-in. However, the TX-NR525 is upgradeable to Wifi and Bluetooth access with the addition of the Onkyo UWF-1 and UBT-1 USB adapters (requires extra purchase).
For additional details on the similarities and differences between these three receivers, including amplifier design and power output ratings, additional network and streaming features, as well as multi-zone capabilities, check out the Official Onkyo Press Release as well as the TX-NR525, 626, and 727 individual product pages. Photo top right: TX-NR525, left side: TX-NR626, bottom right: TX-NR727 © Onkyo USA.