I'm using a 2.5 years/old machine, haven't updated since summer 2006...it's a C2D E6700 2.66 mhz, 4GB, nVidia 8800GTX 768 MB.
In general, you'll want to:
- Use the cpu with the fastest clock you can afford. Faster dual core in FSX is better than a slower Quad. Of course, provided you are comparing same generation machine. An i7 is surely faster than a C2D even at the same clock speed.
- Use card with lots of VRAM. Stay away from SLI/Crossfire solutions, for FSX is better to buy a single fast card than 2 slower cards in SLI.
- Buy good branded memory chips, and pay attention to the speed specs. There are some performances to be gained by tweaking the memory timings. With i7, it's best to buy 3x2GB chips sold together, to exploit triple channel DDR.
I'm not sure I'll be able to suggest a specific brand/model/price. I always built my PCs myself, which is of course usually cheaper and you can select exactly what you want. But my next one might be the hopefully upcoming MacPro with the new Nehalem-derived Xeons...
