in order to have 2 active video cards, you would have to choose "extend my desktop to this monitor". that means, that if your v5 was your main screen, the v3 would have to be your secondary monitor. therefore, you would not be able to see what's on the main screen on the secondary screen. also, i highly doubt you'd be able to activate the tv-out when it's not the primary display.
so in other words, i don't think you can do that.