Mac Mini has slowed to an unbearable crawl!
Before I even saw your DropBox Link, I was about to say it's DropBox Syncing the Files ON your Computer (MacMini) with your Online DropBox Account. This happened to me, as well. I emailed DropBox and they said it is normal during File-Sync. I went into DropBox Settings in the MenuBar and UnChecked All the Folders, so that the Files don't have to be on my Local Computer AFTER they have been Uploaded to DropBox.com (So, they were only needed locally to initially upload to DB without uploading via the website/browser. This is helpful if you have many Folders and Files inside other Folders.) Since the Upload was successful, I also turned-off DropBox Opening at Computer Startup.