I'm thinking about getting a Maxtor d740x 20gb. The thing I would like to know is if the 80gb model is faster. I know that the 20gb model uses only one side of a platter with only one head, while the 80gb model uses 2 platters and 4 heads. Does this make the 80gb model faster? Or are all (20gb,40gb,60gb,80gb) the drives in the d740x line the same speed? Thanks for your help guys.