yes, when you run something that uses AGA, the graphics card will go to sleep and the RGB port will output the program. then when u quit it, the rgb will sleep and the graphics card will continue it's work.
explanation in simple words lol
I see u don't have a card right now, keep in mind that some have a scandoubler input, and will make the change automatically. ofcourse u will also need a scandoubler...
nice cards for the A4000 are: piccoloSD64 , CyberVision64 (not the 3D model) and the picassoIV...
If your monitor supports the 15hhz signal, there might be a chance to get a card like the above, use a small convertor to make the rgb port to vga and feed it to the gfx card. maybe since your monitor supports 15khz it will display like it is coming from a scandoubler with automatic switching...
someone else tried that before?