Hi Mick - I continue to make progress with Cubase. The basic manual is nearly 500 pages and there are subsidiary manuals for the VST instruments - in my case HalSonic and Groove Agent - the latter taxing my brain cell in a manner it is unaccustomed to. The VST amp rack is pretty impressive too (remember that Yamaha bought Steinberg), loads of amp modelling and effects, although I still find it easier to run guitars through the Zoom pedal in analogue mode to get the sound I want. But that is just a personal preference.
If you get a Yamaha THR then that will be your external sound card and the interface with Cubase/Ableton. What took me ages to establish is that the DAW can only talk to one ASIO or sound driver at a time. That means, for example, that if you are running an instrument into the DAW with a little Yamaha or in my case with a little Behringer USB mixer, then the sound can only come out of that same interface, unless you save the project and then reallocate an audio device to play it back (not recommended) - your computer sound card is not accessible, although, of course, you can use that as your audio in/out if you don't have a digital USB/Firewire interface.
I have since upgraded my MIDI interface, 'cos the eBay one was not reliable enough, and bought a Steinberg UR22 which is also a cracking little ASIO interface. So now I have a choice - I can use the Behringer or the Steinberg, but only one at a time. No problem really as I can only play one thing at a time anyway. Some would say even playing one instrument is a bit beyond me
Hope this helps a bit!