fsx loves a high clocking cpu.. if you are not overclocking you should go for the highest cpu clock you can get, nomatter 4 cores or 2 core.. i do think 4 is a better choice. but a 2 core with a higher clock speed will do bettter..
need at least a mid range gpu res quality of the ati or the fps of the nvidia... fps vs res....? always hard to choose
one of the best bangs for your buck would have to be an ssd drive as fsx needs info quick. it was the best fps gain i saw on my setup over all hardware upgrades i have done...
keeping the computer running cool is a must.. you will take a hit on fps with a hot cpu.. keep its temp down...
E.C.O water cooler 80$ my temp has never gone past 55c
gigabyte/2oz copper boards i like.. great overclocking for novice "smart 6 turbo boost" i wouldn't go to the highest setting..
ati 5770 or higher
intel/SSD drive... O/S "windows 7" on the same hard drive as the fsx and all its addons, try to keep the computer looking for all the fsx info in one place..defrag defrag... "but do not defrag ssd. only defrag a hdd" ssd wont let you any way but dont try...
Sounds all right just be aware if you go with a LGA 1156 motherboard that it is a dead socket. I would consider the HD 5850 as it has good bang for your buck. For the same reason don't consider the HD 5830. Intel has great SSDs but they are designed for the server market more than consumer. I would consider crucial or corsair over intel.
Nvidia doesn't have a DX11 GPU in your price range as of yet unless you want to move up to the 470. so for now i recommend ATI
When are you gonna purchase this system? If it will be a while you may want to get an intel 1155 motherboard and see what Nvidia's DX11 offerings are at that time. If you need this sooner you may consider an AMD black edition CPU as those are easier to overclock.
Yes, with i5/i7 you're good.
What about your monitor? size?
HD5770 is good, even with high resolution like 1960x1080, but for a long term HD5850 would be great. makes ure you got a high quality PSU for your PC.