Try disabling the under water effects (light shafts (and maybe, just maybe, volumetric fog)).
Nice rig, btw

, can't any better than that
You didn't say anything about Antialiasing or Texture filtering forces from the driver...
Not to forget, 9750gx2 actually uses SLI although is just one card. So it could be an issue related to SLI.
There is something important that changed in patch 1.2: true resolution rendering. So there could be thing related to light shafts and the big resolution. What resolution are you using?