If you want the card to last, get the 8800GTX, you'll be able to squeeze 4 years out of that mofo easily, you can overclock down the line when the performance at 1280x1024 starts to drop down (which won't be for a long time still)... heck, the 9700 Pro is still decent today at 1024x768 or even 1280x1024 if you tweak your games and play with the settings (as well as optimize the OS) a bit, I know a 9700 Pro can own Half Life 2 at 1280x1024 and it can play Doom 3 at 1024x768 high if you tweak the config files...
I say buying a 600$ card for 1280x1024 is not overkill because there will always be games in the future that will put the card to its knees at 1280x1024, at least I'm going this way, I'm getting a Core 2 Duo (I'm thinking E6600) on a 680i motherboard and a 8800GTX to play in my Dell 1800FPW (1280x1024) but I'll keep the computer (only upgrading to a quad core when needed) for at least 4 years, I know that with the power of the 8800GTX, I'll be gaming happily at 1280x1024 for a long time...
That being said I am incredibly tempted to shell the 800 bucks on a Samsung 244t-bk monitor but I'm happy with my 18 incher, 4X AA at 1280x1024 is already incredibly smooth for me, hell, no AA still looks fine to me, the only thing I can't stand is non native resolutions.