I just got a new machine for FSX myself. After allot of research, I went with i7 4790, GTX980, Z97mx gaming 5 motherboard, I stuck with 8GB but I spent money to get very fast ram as opposed to 16GB but it being slower. New case, liquid cooling. I am very happy, my old machine was 6 years old so needless to say I have seen a huge improvement.
I forgot to add, whatever you decide to get, get an SSD for the operating system if nothing else incredible speed improvement. I hit the power switch and my machine is up and ready to go in literally 20 seconds, I hit reboot and 30 seconds later ready to go.