I recently purchased a 2013 21.5" iMac from Best Buy, base model, and am pleased with the performance of it. However, going from a MBA with a SSD to iMac has been an adjustment. I've been thinking about returning my iMac for a BTO one from Apple that has the SSD, here are a few simple questions I need some advice/help with! 1. If going the BTO route with Apple, should I get the 256gb SSD or 512? If I decide to get the 256gb SSD, can I later replace it with a higher capacity SSD or would it be better to order the higher capacity to begin with? Money is a strong consideration, would like to get the 256 and later upgrade it myself if that is possible. 2. Would a better option be to buy a 480gb SSD, hook it up via a mSata USB connector, and use that as my startup disk to run my computer off of? Instead of running my current computer on the HD, I would hook the SSD up and run my computer off of that. Thanks in advance for the help, I will be graduating college soon and I want to get the best option now for many future years of use.