The bottom line is to do all this on the Amiga and one SVGA monitor. I feel sure this is going to be fairly straight forward once I know how.
Cheers,
JaX
A somewhat different approach, and a good reason to invest in a new LCD monitor:
Buy a LCD monitor with a composite input on it, or perhaps a full TV/monitor combo. I've got a 17" widescreen LCD displaying the CVPPC output as 1280x768 WXGA, and a RGB SCART cable to display AGA modes. Works perfectly, it's even got PiP

IIRC there are/were also CRT monitors with Composite/S-video inputs and TV-tuners on the market.
-Paul