What you want is a DX9 compatible card with a Mac ROM, preferably with at least 64 Megs of memory to pick up the speed of Leopard with all the bells and whistles turned on. Basically a Radeon 9500-9800 or X800/850 or a nVidia 5500 or higher. The 5200 technically meets the specification, but is just so slow it probably wouldn't be worth it. I think the Cube has a 2x AGP slot, so you'll have to get a 2x/4x card. I don't think 8x cards work in 2x slots. Yeah, before anyone says it, I know DX9 doesn't apply to Macs, but that's the easiest way to describe which cards will work under Core Image/Core Animation. You may also have to do some modding to get any video card with a cooling fan to duct air properly in the confines of a Cube and do some electrical mods if you want to use a card that draws additional power from a molex connector.