Hi, I'have an old gaming pc that will work great with fsx.
Specs:
Intel core 2 q6600 @2,40 ghz
Asus p5b
AMD radeon r7 250 (first a nvidea geforce 8600 GT)
2 gb kingston ddr2 800
Stock cpu cooler (still:25,34 C stressed: 38,45 C)
The game will run on graphics on ultra 1600x900x16 wth a target framerate of maximum of 40 (on ground wil the fps on 23 to 32 fps and in the air 34 to 40 fps)
REX and EMB series are installed