well, a pci card isn't a problem for gaming, because directx and opengl use an overlay, so the video is coming straight out of the gpu out to the monitor
the only place a pci card really suffers is that it takes longer to load data into the video memory, and non-accelerated graphics (visualizations in wmp are choppy, and even moving windows can be choppy, and full screen flash video is a nightmare with a pci video card.)
You can get a x1300 for under $100 for your pci slot, and it will beat the piss out of the onboard.
the x1300 (in fact, anything in the radeon line, i believe) has onboard mpeg2, mpeg4, and h264 decompression, so watching movies will be fine on it. The only things that really suffer on a pci card are those i listed above.