Hello, I'm a current iMac user looking to upgrade to a mostly-maxed-out 5K 27" soon. The only remaining question for me is HDD configuration. To give you some background, I do web design, photography, and video editing (4k). Currently, all my files fit on my iMac's 3TB drive but I'm almost out of room. With the new iMac, I'm leaning toward 512 internal SSD for applications and moving all my work files to a 4TB external. That's the big question. At first, I shopped for single non-SSD Thunderbolt 2 external drives but noticed that even with the super quick Thunderbolt connection, the external HDD itself would be the bottleneck and possibly not fast enough for editing 4k. It seems the only use for Thunderbolt would be if I was doing a RAID 0 for the increased HDD speed. Am I correct? What are my best options for a 4TB external that would actually be fast enough to edit 4k video over, while trying to keep costs down (no external SSD)? I'm also not opposed to USB 3.0 if there was a combination that would work but I suspect thunderbolt is the way to go for the speeds I need. Any insight would be appreciated, thanks for your time.