game requirements say : Geforce 6800 or Radeon 9600, lower cards may work but at degraded performance

 

runs best : Geforce 8600GT/8800GT Optimal or Radeon X1900 GT and higher

 

your card is in between these specs so it should be fine but usually what they recommend is the best way to go

As long as the card and the monitor have the same interface, it will work. Sometimes a new monitor won't work well on an old card that cannot support the higher resolutions of new wide monitors