I had two crossfired video cards (ATI Radeon HD3870) which although I thought it was adequate, it gave me poor performance in FSX. To get a balance between graphical quality the speed, I had to drop down the settings. However Thanks for  the suggestions from you guys, I was informed that a single card would provide me with a better performance for my FSX comapred to the crossfire. So I did. I don't know if this is consistent but with one card I was able to max my graphic and scenery settings and placed my FPS to unlimited with no problem (yet). I even increased my resolution to 1280x1180. The improvement was unbelievable. Is there any performance test I can do to ensure that what I have is for real and that there is some technical explanation for this phenomenon?

I had my FPS set at 50 right after installing only one video card. After setting it to "Unlimited" however, I noticed my FPS cycling up and down the range sometimes reaching 99.9 FPS. Is that good or bad? Nonetheless I will follow your suggestion and set my FPS to 25. BTW, can I set my "buildings" and "trees" to max in the fsx.cfg to improve landscape graphics?