I agree with 003. I'd go with the highest-end videocard money could buy. But that's just me. Sure you could get by with a 7800GT it's a great card.
My main concern is maxing out settings for games like UT2007 & Elder Scrolls: Oblivion
It's a tough call... But i'd go with the latest and greatest. The only problem is, "That label only lasts for a few months." But oh well.