I used to use a 960 until recently, the best thing I found to do with that card is to cap the frame rate to 30fps, then it kinda runs quite smoothly even with fairly high settings, so you could give that a go, not 100% sure that will help but no harm in trying.
Look for this file autoexec.cfg in your DCS Saved Games\DCS\Config folder and add a this line:
options.graphics.maxfps = 30