Well, this little project is finished and working. Quite pleased that measured offset dropped to <1 mV on both channels once the amp was in the chassis and wired.
This is where I state that it's the best amp I've listened to, and it is... Unfortunately, it just highlights any shortfalls with the speakers. The Mission 773e have never performed better or sounded clearer. However, you are just as aware on how quickly these speakers lose the plot with more complex music... In the long run I hope to match the sound of the Sennheiser HD-650 driven by "The Wire" se-se HPA, the FH3 are my first try at achieving this...