From the Prepar3D Application Support » Hardware Specific Questions came this post from arecee;
"Kalop, I have an older system and I'm quite pleased with the way P3Dv2 runs. My system is Q6600, 4 gigs RAM, nVidia GTX660 2 gig, Win7 64bit. Most of the sliders are in the middle to mid-high (except traffic, airlines @40% others are off). I not using HDR only becuz I don't like the way it looks (too dark).
I am using nVidia Inspector for certain options, lock frame rate at 30 and run FPS in P3D set to 33. Other than that, P3D is pretty much a plain vanilla install (no tweaks).
Main planes I'm using are Iris C-27J, Rollus Mirage 2000 and Dino Cattaneo's T-45C, plus WOAI for airline traffic.
My FPS are stutter free and stay in the upper 20's, even on this 7 year old system.
Compared to FSX... well I can't even bring myself to use FSX anymore.
Hope this puts some of your concerns to rest."