Jamie, thanks for the very useful comment. I'm also looking to get into editing XAVC-QFHD 4K at 60mbps from the Sony X70. I'm looking at portable Thunderbolt and USB 3.0 drives, and my question is, will a 5400rpm drive handle that? Or will a 7200rpm be necessary? I'll be editing short documentaries, so no graphics intensive, multi-track stuff. I'd like to stay around $200. Thanks so much!