Do you think I can achieve ~35 fps on high?
At 1920x1200 I run high textures, 2xMSAA, high FXAA, 16xAF, SSAO, everything else medium. After much tinkering, this is what works best for me. I get a constant +60fps, averaging ~80fps. If I turn MSAA off, I can get the same fps with everything on high, but it doesn't look quite as nice with the jaggies. You have a single 6850 at a slightly lower resolution, I'd say 35fps average on high (AA off) is probably doable, but that's hardly a playable framerate for online shooters. You should start with medium and adjust from there. But don't worry, medium in BF3 still looks really good.