I’ve received a few emails requesting recommendations for graphics cards…unfortunately I must admit: I do not know which graphics cards will improve framerate the most. The benefit you get from a new graphics card depends on the other components of your system. Also I haven’t tried every graphics card so I don’t have good hard data.
I will suggest this generic advice though: for nVidia cards try the 6600 or 6800 rather than one of the FX series cards. For any card, make sure it supports DX9 pixel shaders (for nVidia this means a 5000 or 6000 series; for ATI this means 9500 or greater, or an x600 or greater). I would not recommend a card with HyperMemory or TurboCache; these schemes use your system memory as VRAM. The cards are cheaper but the performance won’t be as good as real RAM.
I’ve also received questions about settings for the best framerate. If X-Plane 821 is fogging up with the new scenery, 830 may provide some amount of relief; we’re working on performance optimization. I can’t say how much improvement we’ll get, but I would recommend waiting for 830 before evaluating your hardware for an upgrade.
There is one setting that can really help mid-level systems: the “world detail distance” rendering setting. If you can run with a few objects, try changing it from ‘default’ to ‘low’. This will cause objects to disappear sooner as you fly away from them; because the sim will not draw as many objects in the distance, you may be able to turn up the object density. In otherwords, you can trade off the density of near objects vs the density of far away objects.
(Also beware of textured lights; they really impact framerate heavily.)