Considering that I'm after a second hand MacBook (pro or air) with SSD, what would the best option be? My budget is £600. As pros at this price won't come with a SSD, part of this money should be used for the upgrade. I know there is not a lot of options, but would appreciate any inputs. My usage is fairly basic these days, but i do enjoy a smooth machine. The ssd thing is essencial. No more hard drives for me. I want to see some flow. Please tell me what to avoid too. Thanks