we still don't know monitor res... why are we arguing over GPU recommendation?
based on the games he plays.
Without a monitor resolution, there's no use in making a recommendation.
If his resolution is 1024x768, all he needs is a 9600GT.
If his resolution is 1920x1200, a 4890 will get its ass handed to it by Flight SimX. Unless your goal is to play with minimal options turned on and where's the realistic flight experience if that's what you end up having to do? Hell, my GTX280 plays FlightSimX pretty well, but I have to make some compromises on quality to do so at 1920x1200.
When you read someones post saying something like, "We need to know the resolution," and it's from someone who has been around here awhile, do some research before making your self look uninformed.