Connect to the HD621 with the Config program and under the file menu, select 'identify' which will give you the firmware version and serial no.

The latest firmware only added 3D pass through capability.

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.