Thanks for the test and overview dubhausdisco. That’s a real shame about the unsupported multiple outs. 
One of the audio interfaces that is recommended on the Steinberg site is the RME Fireface and this has 6 or 8 outputs.
I would imagine that all of the outputs work from Cubasis with it or it would be worthless shelling out £800 for.
So, as you say, probably a software issue. Don’t know if Steinberg have to explicitly code for each supported audio interface or something.
Looks like the keyboard stays until there is a Cubasis that works with a reasonably priced audio interface with multiple outs. Or maybe Auria will beat Steinberg to it and implement a full midi spec, in which case I know where my money is going since it already supports the Akai…
Cheers for your help.
Stevo…