With that monitor, you should be able to increase your resolution at least one notch and maintain framerates or increase. With a GF3 Ti200 you may even be able to run 1280x1024 32 bit color and 2x FSAA for a very good quality picture. At the least you can run your current resolution and color depth with as good or better framerates AND FSAA to make it look even better. But with a decent 19" monitor, I think you should jump up one notch. Your CPU may keep you from seeing much higher framerates... but your video card should allow you to go to higher resolutions and increased filtering and quality and maintain playable framerates.
Well, the eye cannot detect individual frames at over 25 fps... but that's if you are talking about a piece of film with no movement in the image. For moving computer graphics without all the effects like motion blur that tv/film has, you can definately tell the difference between say 30 fps and 50 fps... I know I can. 60 fps is what I believe the limit is given the environment. Basically, if you can hold 60 FPS at all times, your game should look and feel smooth at all times. Personally, as long as my framerate in AH does not drop below about 30fps it plays just fine for me. I really don't have a problem until the fr drops below about 20... then it's difficult to control and shoot.
