Sorry to burst your bubble man, but I built my System a few weeks ago primarily to run FSX. I would consider my system very high end, considering I have it clocked at 400x8 (3.2GHZ), and FSX runs HORRIBLE on my system. On full graphics, with 8x AA, 16x AF, 1680x1050 Widescreen, with my 8800 Card, I only get 6-25 FPS. Most other high end systems have the same result. Its not because of the PC, but because of the coding in the game.
FSX is set up to run primarily with DirectX10, which will not be available until December. I have heard that FSX runs a little smoother on Vista, but I am not sure. However, what is interesting is I can run Flight Simulator 2004 at over 100FPS with the same Graphics Options (maxed out) as FSX. So FS2004 will run awesome on your system. Im keeping my fingers crossed hoping that DirectX10 will solve the FSX Problem. I would have to guess and say that currently the only system that can run FSX so that it is flyable, would have to be a Quad Core Extreme with SLI with dual 8800GTX's OC'd to the Max! Its ridiculous, I know, but search around and youll see that there is very few PCs that run FSX very well....
Hope that helps!
Good luck with everything...
-Joe