Well I think you need more memory, like 2GB to run a healthy computer these days. 1 may slow down your system by a lot. Also you might want a bigger PSU, at least 430-450W. For the card, if you can go for the X1950Pro, it's better than the GT and around the same price
Also you can get a little cheaper Motherboard, that would be just as good. Unless you are looking to do Crossfire in the future.
MSI K9AG Neo2-Digital or GIGABYTE GA-M61P-S3. Those are both really good cheaper boards you can use