More specifically, the quicksilver dual gig versus the new MDD dual 1.25. I am pretty sure the newer one is an overall better machine, but how much better? It is $100 more than a refurb quicksilver and the QS has a superdrive and more ram. Would I notice much of a speed difference between the two? Does cache really make a difference (I do ProTools work, and am anxiously awaiting PT6 for OSX) I also think that with audio number crunching that the DDR and faster bus speeds would help that alot. I am pretty much leaning toward the new MDD, but am wanting to know if there would be any reason to get the older QS refurb.