4TB drives are only $100 these days. Come Black Friday, you might be able to find a 6TB for that price. IF YOU'RE NOT BUYING A BACKUP HARD DRIVE, YOU MAY AS WELL KILL YOURSELF. You need a backup drive, generally 1.5x the size of your working drives (if you want versioned copies). If all you do is game on the thing, do a drive clone once a month. Automatically schedule it if you're too stupid to remember. If you do work on it, you want automatic hourly backups.
Other than that, will a 550W PSU really handle a 1070 as well as everything else?