Booting off a SD card and placing my apps and programs on one. What do I need to know? I want to keep the SuperDrive, as I use that often enough to require one right now, in the future I might remove it and place a SDD in it's place. What is the speed difference between a SD card and SDD? Also what time of SD card should I get. I want something that is fast but also cheap. But I really do want quality rather than price, so something that is quite nippy. I'm looking in the 128GB range. Thanks!