Hey guys, I'm about to buy myself a 27" iMac. I need the best possible performance for video editing, so I don't want the Fusion Drive as a pure SSD is still faster. But I don't want to pay Apple's crazy prices for a 512GB SSD. So, my question. I've heard that it's possible to hook up an external SSD via Thunderbolt and install OS X on it? Would this method be any slower than using the internal SSD? Would seek time be affected? I need maximum performance for video editing, so don't want any bottlenecks. Any info appreciated! Cheers!