Yes, although SiS isn't a video card, since it is just an integrated graphics chips that uses your systems own memory for itself, instead of having its own dedicated video memory. Most integrated chips are below minimum requirements for adequate Dreamcast emulation, and the only exceptions are some integrated chips from ATI and Nvidia (Radeon Mobile and GeForce Go line respectively). You would need a fairly decent video card, which certainly doesn't have to be top of the line. Any ATI Radeon from 9800 and up as well as any Nvidia GeForce 5700 and up will do more than fine. What matter in emulation of any kind most is the CPU speed, everything else is more or less secondary and not as important in terms of smoothness and overall ability to render the DC graphics properly. 512MB of RAM will do fine, although having more than that never hurts.