These are the firmware note I could dig up:

DSP6000 Product Firmware Release 5.40 (2011-10-31)

Software Fixes - Useful - May be useful to upgrade but not essential
Aux legend becomes SLS and VCR3 legend becomes Aux
Aux/SLS source defaults to 4C comms type
Optional support for M80 remote
Improved processing resolution
Better integration with two way speakers in theatre systems
Crossover improvements

DSP6000 Product Firmware Release 5.20 (2007-11-16)

Software Fixes - Useful - May be useful to upgrade but not essential
Improved crossover.

DSP6000 Product Firmware Release 5.10 (2006-08-02)

Software Fixes - Useful - May be useful to upgrade but not essential
Volume control responds according to system address - relevant to some two-room systems.
Latency through DSP speakers unified at 7.5ms.