1. GTX 285 is best for FSX, however
Nick stated the Radeon 5870 comes close. Furthermore, in all other benchmarks the Radeon 5870
is much faster than the GTX 285 while also having DX11 support.
2. The Radeon 5850 is slightly slower than the 5870, not sure about FSX performance however, but still beats the GTX 285 in the majority of other benchmarks. I think the 5850 is extremely good value although it might not be the best for FSX. For the price range the 5850 still might beat the GTX 275 in FSX (I'm not sure).
3. The GTX 295 uses two GTX 275 cores and slower memory so it's a waste of time in fsx, however it's faster than the 5870 in everything else.
4. I think the weakest point in your system is the processor, and memory however. Consider getting a cheap P55 (ASUS, MSI, GIGABYE) board, Core i7 860, and 4gb of DDR3-1600 - make sure to overclock it for best performance with a nice cooler.
Last edited by Slotback on Mon Oct 12, 2009 12:05 am, edited 1 time in total.