No question - that video card stinks for use with Motion. You probably want to add some more ram as well but, the video card is what is really holding you back. barefeats.com has a new test of the 6800GT and it appears that it is the best bang for buck option right now. The 9800 is also good but, the 6800 is faster and costs about $50 more.
or you could buy my 9600 since I am getting a 6800GT :)
gl
