I have that card in my triple monitor setup, but it is set as my PRIMARY card.
I am reasonably sure from my talks with tech support at ATI before I purchased the card that any and all multimedia functions of the ATI card will NOT function unless the ATI card is set as your primary.
The folks at ATI tech support were very kind in responding to my questions even before I actually purchased sads vid card.
You may want to run this scenario by them before you put down your cash on it.
My take is that the the vid in will NOT work in your proposed setup.