Oops, sorry. I miss read the DirectX Diagnosis you posted into saying you had 256 RAM for your comp. My bad. In that case, I don't know what to say, other than possibly update your drivers, because people with stats around those of your behemoth of a machine have posted screenshots that look identical to the official ones in terms of quality. Since you have an Nvidia card, its not the probelms ES has been having with ATI cards and AA. That is the type of computer that ES is expecting to run the game at the highest or near highest quality. In fact, ES uses the 6800 series on all their "showing off the game" machines.
"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."-Albert Einstein