Do any of you have experiences with the new Mac Pros? I'm trying to decided whether I need a few more tenth's of Gigahertz or not. My plan right now is to get the 8-core 2.8 Ghz model with an 8800GT GPU and I'm going to order an additional 8GB or RAM from another supplier. So, is the slight increase in speed useful? Is it worth the several hundred dollars more I'd pay for it?