You're kidding. Right?
You're worried about one of the top video cards playing a year-old game.
I can play UT2K3 with a Radeon 8500 and a dial-up connection with reasonable smoothness. OK the ping times kill me but the game does play smoothly even on my old hardware. Much better performance than most online FPS games (with a dial-up connection). I was quite impressed with the performance. Gameplay and visuals were another matter.
I don't think you will have any problems. If you do, just overclock that Barton a little. Fix you right up.
<b>56K, slow and steady does not win the race on internet!</b>