I have a late 2007 Mac Pro that I want to replace with a 27" iMac. One reason for upgrading is I have a bunch (2TB) of family videos I need to edit in iMovie. Currently iMove brings my MacPro to it's knees, so I haven't done anything in a while and I need to catch up. I also use Aperture a lot. Everything else I do on my Mac is low performance in comparison. I don't do any gaming. No 4k video, just HD. I'm leaning toward an iMac with 500GB SSD and external thunderbolt storage. 3-4TB should be more then enough. I'm looking for some advice on what to get for external storage.