It is possible to use both cards with the XFree86 nv driver But this driver does not support (TV out as far as I know). Both video cards work with this driver. This is with a standard XFree86 installation from the ports dir.
To use the TV out i think i have to use the NVidia driver.
With the newly released nvidia driver which supports TV-out the error line i get when starting X is: Failed to initialize the NVdriver kernel module...............
Did have this error line???? And of course (how) did you fix it...
Greetings and have a good day