I've read that the human eye can't see anything faster than 40-45 fps, but on the other hand if your refresh rate is below 65, most people get headaches looking at there monitors for long periods of time. The trick is to have it steady.
Set your refresh rate at 75-85 in both the computer monitor settings as well as the game settings. Most of the newer card run 512 resolution BETTER than the 256. I couldn't get it steady at 50 fps set on 256, but have no trouble running steady at 75 fps at 512 (9800 pro 128 meg card ) I thought that if I used the lower textures I could run the graphic higher... more eye candy... but it turned out it was much better on the higher res.
The antialiasing is what kills most cards. The higher the number the more smoothing you get, but its makes your card work for it. Best thing to do is to try different settings and see works best for your set-up.
I run 1280x1024 with the 512 res, and have my sliders turned up to about 80-90% graphics side in the game and run pretty steady at 75 fps. Your milage may vary
