Hey folks, I'm going to be purchasing a 20" iMac soon, but am unsure about how much video ram I should get with it. Does anyone know what the benefits of having 256mb of video ram over the standard 128mb are? If it matters, I plan to screen span with a 19" CRT and play a moderate amount of windows (hopefully) and mac games. How exactly will more video ram benefit my user experience? Thanks folks!