I agree with Scuddie on this (suprisingly). IF it's giving you honest-to-god headaches or making your eyes sore, check to see what refresh rate your monitor is running at, that is if you're not running an LCD. Bumping up the Hz to the max for that resolution will usually fix eyestrain problems. I'm being dead serious here, and not trying to poke fun at your situation. Since you're using ATI's questionable software, look for a program called Reforce. That little treat will autodetect max hertz ratings for your card and monitor combo, and make sure they are automatically applied whenever you want to run something at a given resolution.
Games @ 85Hz @ 1024X768 are just fine.
I run everything I own in 1024X768 anyway, (9800XT, I run FEAR & Q4 in it just fine) and I honestly don't see why in the hell you would NEED to run something higher than that unless you just want to gloat and/or show off. If you're looking for topped-out 60FPS in every single situation with 8X or higher AA and 16X AF, and all that jive running the latest games, you're gonna have to get into a duallie 7800 setup with the absolutely lowest latency system ram, and hard disks faster than raptors.
Besides, no one's ragging on you. It's the honest-to-God truth, turn down the AA and AF. Does anyone remember when Deus Ex came out, and those who were fortuate enough to have a Voodoo 2 based or higher card would get silky-smooth framerates, and everyone else who had the Riva TNT and Geforces had framerates in the tank? Not in the tank, in the damn toilet! Think of it this way. Perhaps the game is simply so advanced that current hardware gets pushed quite hard. The next line of hardware will be able to render this without breaking a sweat.
And then again, you get what you pay for. Since you didn't buy dual 7800's, dont expect dual 7800 performance.