It would also be helpful to have a tutorial on setting the Montage with Cubase when not using the Montage as an Audio Interface, but rather using a third-party audio interface.

Thanks

@ Tarek, you don't need a guide for that I can write that in a sentence or two:

Connect the Left/Right audio outputs of your Montage to your third-party audio interface (if it has more than two inputs, you can additionally connect your Assignable Left/Right Outputs to those additional inputs)... make sure you route all Parts to either "Main L&R" or "Asgn L&R". In Cubase set the recommended driver as your ASIO Driver.
Please refer to the documentation of the audio interface for info on the driver, and use your audio interface.