This is strange: you had 20 fps at Zurich with your previous video card, now you upgraded to a 1GB card, and fps went down to 10-14 ?
In your case it looks more like a driver problem. Are you sure you are using the same FS complexity settings as before ?
On FS9, fps like that are really not normal, and not how the scenery should run. I have much better fps (from 25-30) in FSX! The only thing that might be able to slow down FS9 so much is either an AI traffic package with unoptimized models and too much traffic, another scenery in the area that creates problem, or an airplane with fps-eating gauges.
Try to diagnose one thing at a time: check your fps with default C172, and no traffic. Then progressively add traffic density, then use your favorite airplane, and see how fps changes.
For AI, I suggest World of AI, which is both freeware and very fps friendly.