C Drive full

Hi Team I am running out of C Drive storage. I have a Samsung 840 EVO 120GB 2.5 inch Basic SATA Solid State Drive as my current C Drive and it literally has 1GB left. I have around £150/$200 to pickup a new one to upgrade it, but have a few questions: What brand/version should I upgrade to...

I was thinking 850w would be fine, but should I go bigger and get a 1000w power supply? I searched google for what people said about how much watts each component would consume. It's my first build so I'm not sure if there is anything else to finding out how much watts to get besides just adding...