At 512Gig the swap file might be slowing you down. Also the graphics update hit is heaviest on the map while near bases with large numbers of radar contacts. To test this watch the HD light during play or bring up the Task Manager Performance tab and play for a little while in a game already loaded, then switch out to the Task Manager and see if the Page File history jumps up and down by a large amount.
On my system with 2G of RAM and 512Vram, I have no swapping at all and once the game is fully loaded, I have no HD activity.
-Pv-
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