With only about 5GB left, and countless data DVD's, on the original PM 160GB HD, I'm going to get a Maxtor Diamondmax 10 300GB for the second drive bay. The question I'm asking now is which one should I use for my main OS? The Maxtor drive has a 16MB cache and I have heard numerous reports of its speed, especially in post 10.4.1 OSX. Does the speed justify a slightly more laborious changeover? Is it really that fast? I had planned to use the 300GB as a scratch/backup disk.. Your 2 cents?