Need to upgrade graphics card on XPS 9000

I purchased an XPS 9000, which came with an ATI Ratheon HD 4350 512MB graphic card.  I run an online program called "Second Life" and need to upgrade the video card.  Their requirements list:  Video/Graphics Card(*2): nVidia GeForce 2, GeForce 4mx, or better OR ATI Radeon 8500, 9250, or better.  Can anyone suggest which would be best for an XPS 9000?

Thank you for your help!