The components that most people here would recommend are the Asus P6T and i7 940. I use both and they are great. make sure you run an x64 OS to take full advantage
You will love the i7 940! Very enjoyable to fly with my current system. I agree 100% DO NOT USE 32 bit OS with a i7 setup! I have learned this the hard way and now have XP 64 bit on the way from newegg. With the large amount of ram now on the new GPU's and the way i7 eats thru FSX you will want to crank up the sliders. The problem is not being able to crank up the settings but the 32 bit memory problem you will have with all the eyecandy you will now be able to use.