So since you think my card is struggling, what can you recommend? Nvidia Inspector has over clocking. I really want to figure this out and since I think we're now onto something.
As I've said, if you are getting an increase of fps by simply lowering the window size (I'm basing on YOUR reports), it's nothing related to the scenery, it's your video card that can't keep up with the fill rate.
Since it's not normal, because FS9 is never fill-rate limited, the only possible explanation is another setting which affects fill rate other than antialiasing, which is only the most obvious one, but not the only one.
And, of course, I assuming you are testing with a default airplane. Regardless of what you keep saying, if we are trying to see if FSDT KORD is a problem or not, you should test the SCENERY, not the airplane. So, again, only reports fps using a default airplane, otherwise you are testing your Level-D, which might be interesting, but not the place here.