The answer is definitely "nope" with FSX, at least for now. Fingers are crossed that things will change with the new version. Gotta remember, the original code for Flight Simulator was started back in the mid-80's and probably just added on to. Who knows if they ever did a "ground-up" rewrite. And back then, no one even heard of add-on GPU's let alone using the crazy levels of RAM we do now.
i5-2500K OC'd to 4.7GHz and Liq Cooled, 16 GB RAM
470GTX SC GPU to TripleHead2Go w/3 19" HannsG digital monitors
Saitek Pro Yoke, Pedals, and panels/Saitek X45/Logitech G15 keyboard
Windows 7 Home Premium