In our quest to find that sweet spot for our beloved hobbie, we have to give (loads) and take (less) with the results to get FSX looking and running as best as our machines will handle. We have all tweeked at some point. We have all upgraded at some point and how we are not all bold (no insult meant) by pulling our hair out, is beyond me.
Anyway, I found a little trick I'd like to share with you, and I'm guess it's not for most but, if like me you run your computer using a TV and not a dedicated monitor, if you go to the settings on the TV, and set the sharpness to 0, then go to NI and drop what ever you use to reduce jaggies by 1 level, in my case thats SGSS from 8 to 4, it makes my sim look the same but it runs smoother. I cannot tell you about the FPS as I am not really interested about them, its smoothness for me.
It works for my setup but I'm not guarenting it will work for you, but it is worth a try. I would also guess it works for FSX-SE and Prepar3D, but I don't have them so I could not guarentee that either. If it does, I'm sure some kind fellow would let us know.
Rich