Sorry, I was short on time and wanted to warn you off seagate.
I would recommend an external drive enclosure and a HGST Deskstar NAS or Toshiba X300 4TB, both of which I've sourced before from Amazon. I recently bought one of these, which I use to house an 8TB HDD made by WD/HGST:
I recommend the LaCie Porsche Design. I have the 8TB version. The Mac model has Mac-type finish in the aluminium. The Windows model is a darker brushed aluminium.
People can say Seagate (which has bought LaCie) is garbage but every company has a bad batch run now and then. Looks and price count for a lot, especially when you can back up with Time Machine.