Easy answer, better yet let me ask you this: Why isn't a system with 4GB running XP faster than a system with 1GB.
What, you though more memory made things faster? There has to be a limit as to how much of that memory is used, right? Why not make 512MB video cards? Or even 1GB video cards? Programs aren't designed to use that much. In fact, most games run perfectly on 64MB. The latest memory-hungry games run perfectly on 128MB. Maybe in a couple years you'll see a large boost going to 256MB, but then again, I just retired my 32MB card and it was playing new games perfectly at 800x600 (that sounds low, but remember I said 32MB!).
<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>