I’m not sure if I understand your question correctly but:
If you want to to record the sound from you vst gtr amp into Cubase in real time and be done with it, then you can insert your gtr vst amp onto one of the inputs of your sound card in the mix console.
- Open Mix Console > Insert vst gtr amp on Input 1 for example (or whatever the inputs are labeled like )
- Create an Audio Track > select the same input you are using
- Press record > and off you go.
Your amp sound will be recorded on the Audio track as you hear it. Any FX or plugins you insert on the input in the MC will be recorded as well.
Hope this helps!
F-