I would wait until 2006. Thats when the big changes will take place. Such as the next generations of cards, Unreal Engine 3, Longhorn, DX10, Pixel Shader 4.0. That is when I am doing my upgrade. No since in spending $2000 in the summer of 2005 if there is going to be such radical changes within a year that it makes it completely obsolete.
P.S. Upgrading your current video card to a 6800 or X800 would be perfect. It would get your PC to 2006 no prob.