I upgraded my power supply to a simple 2.5A one when the original one gave up after 3 years of daily use. Have had no power issues since.
My internal HDD has been upgraded from a 4Tb to an HGST 8Tb 7200rpm with no problems. I also regularly plug in an external USB 8Tb drive (I have 3) and play high bitrate UHD movies (some files are >100Gb), also with no problems.
These 4K movie rips take up heaps of HDD space!!