Depends on your budget really, you could go all out with a water cooled card...something like the Sapphire Blizzard X1900 XTX
Expect to pay around £400 for one...
Try googling "Graphic card reviews" theres alot of unbias IT information out there. Personally I have been disappointed with my ATI card (I cant stand the catalyst software/drivers, nothing but trouble) and wouldnt buy another one, how have you found yours?
Also check out the flight sim websites, alot of them do hardware reviews especially for MSFS users, so you might find exactly what you need that way.
