Yes, a 6800GS should be able to handle that res. I was playing that res with a friends 6800xt (not unlocked). You may be able to pull a little bit of AA out of it as well.
AGP or PCI-E? If agp, you can unlock pipes to a 6800gt, which will give you even better performance...but it plays it reasonably well at 1280x1024, not sure about maxxed settings though...with no AA or AF you could probably max, but im sure you can have them on and find a happy upper-medium, just takes lots of tweaking and a long time staring at the loading screen as you try each slider one by one...
I figure I paid $200 plus a $25 MIR for my 6600GT when it first hit the market and this 6800GS whether I can unlock the other pipes or not will be faster then my current 6600GT and most surely my ATI 9800 Pro.
Although, I would jump on the 7600GT AGP if I could find it for a similar price, but the lowest I have found it was $185 shipped at ZipZoomFly.com
Thanks to all, I think I will jump on that deal and see where it takes me from there.