I'm looking at buying a base 27" refurb from Apple (to replace a mid 2010 13" macbook pro), I like the price but know the standard 1tb fusion drive is less than ideal. I'd like to use a SSD in the machine and upgrade the RAM myself. What is my best choice? 1. Get an external SSD and usb3/TB3/USBC as the boot drive? 2. Pop the machine open and swap the fusion to a SSD? Would I be crazy to open a "new" machine? 3. Pony up for a new one with SSD?