Bottleneck in Compaq desktop

[RollWave]

This comp is a xp1900+ palomino, with 1gb of ram and currently has a crappy Ti200. I was wondering what is the least expensive card would go right up to or become a bottleneck. IE what is the cheapest maximum upgrade solution?

 

[edro]

Radeon 9600 for about $150.

or

nVidia TI4600 for about $150.