a 4870 or 4890 would go well with your setup, but again, it all depends on what resolution your monitor is set to, what size your monitor is and what your budget is. Also, is it for gaming? if so, list the games you play
If you want something cheaper try to find a ATI 4730, they are sold in Europe & have slightly less performance than a 4830 (on average 2-4%)
The 4730 would be the minimum for that res, unless the game is very old.
I would recommend a 4770/4850 to do a proper job.
From your link the 9800GT would be the minimum, the same performance as the 4730.