when I bought mine, I selected the **320Gb** 7200rpm, and never look at 500GB as I always said to me that, for big space, NAS Server or External 1/2Tb would be the best option, as when I'm moving, **I really don't need that much space**, only when I'm at desk. So, instead, I upgraded to a [240Gb SSD from MacSales][1] (OWC), and ... WOW, what a speed! what a thrill to use this drive! no sound, no moving peaces, faster as you can dream. [See here a normal drive (HHD) versus an SSD booting up][2] *image below* blue drive is the SSD drive, outside drive is the WD Scorpio Blue 320Gb ![alt text][3] then I also bough a 2,5'' Bus powered enclosure to put my 320Gb native drive as now I use to keep my recent stuff including photos. [![enter image description here][4]][4] hope it helps. [1]: http://eshop.macsales.com/shop/internal_storage/Mercury_Extreme_SSD_Sandforce [2]: http://eshop.macsales.com/Video/SSD/Performance_Test [3]: https://i.sstatic.net/EaFcJ.jpg [4]: https://i.sstatic.net/mZSnq.png