I am planning on purchasing a Macbook and I've been looking for things to get for it. So far I am taking my 19 inch LCD Screen, a 160 gig WD Passport, planning on purchasing a Radtech bluetooth mouse, and a STM bag. Now I just need to find a nice external hard drive for backups and Time Machine. Any suggestions? I want it to be affordable but good quality. Also what size should I get?