I cannot comment on the Virtual Cable (yet) but if you downloaded and installed Voicemeeter...
1) Set Voicemeeter as default audio device in your Windows Control Panel Sounds
2) Go to Sonar "Edit > Preferences > Audio - Devices" and DESELECT your current interface ins/outs and select all the Voicemeeter ins/outs
3) In Sonar, set up an audio track and from the input options list select "Stereo VM - VAIO 7/8" (or something like that)
3a) Click the "Composite" button on the Virtual Output bus in Voicemeeter (output bus "B") which will provide a prefader tap of the virtual input bus
4) Arm the track and press playback on your youtube vid. It should be playing back in the Voicemeeter Virtual Input section (and the VM meters lighting up) AND you should be getting signal in the stereo track.
If all that is happening then all you have to do is start recording.
Cheers.