|Your VGA card will work as long as the mobo you buy supports the card type regardless of CPU. I am assuming the Q600 is PCI X 2.0 - so for optimal performance of the VGA card you would want at least that or higher. |
The AMD crossfire X is specific to the AMD family video cards (RAEDON), so you wouldn't be able to add anymore Q600 cards or utilize nvidia SLI (Nvidia's version of crossfire X) to have multiple nvidia cards installed on the system. So, if you wanted to utlize 2 (or more depending on the board) video cards, they would need to be matching AMD Raedon's.