Onkyo USA introduced Wednesday a pair THX Certified Select network A/V receivers including Onkyo’s first IMAX Enhanced Certified 9.2-channel model, the TX-NR797. The Onkyo TX-NR797 ($699 suggested retail) and Onkyo TX-NR696 ($599) both support the Dolby Atmos and DTS:X object-based surround sound formats, 3D sound…