Sorry if this is obvious to the people "in the know" but I just ordered a Mac Pro (specs in my sig) and along with it I opted for the X1900XT as it seemed like a good card for the money.. though I hate to wait a month for it. I am curious however, the specs on it seem to be better than those of the Quadro 4500 which sells for over $1200 more.. what gives? What's so special about the Quadro4500? is it really worth that much more in terms of performance? thanks for baring with a low-tech geek like me..