Hi there, I'm planning to order the 2.6GHz model with 16 GB RAM. My debate is between the 512 and 768 GB SSD drive. Is it worth adding $500 for the additional flash storage? I will be using the computer for video editing, so I'll be working with lots of HD footage. But would it be better to save the money and rely more on external drives for editing/media storage? Or just spring for the extra internal storage now in case I need it? Thanks for your feedback!