I am trying to do a little research on adding external drives to a 722k. From what I can find, the 722k has a 500GB internal drive. As this drive fills up, my DVR gets more and more sluggish to respond to commands. In addition to that, I would like to have a little more recording time for keeping some things on it long term. To keep things peppy, I am considering a 7200 RPM drive with a good cache on it. But knowing Dish (and Direct for that matter) probably put the cheapest lowest spec drives in their units they can get away with, I wonder if a 7200 will actually make any noticeable difference (especially since both would still be going out over USB2). Has anyone seen any tests showing 5400 vs 7200 drive differences on Dish DVR's?