So recently I wanted to build a computer and this is my first time. I am unsure whether the power supply is enough or too much. I am also to find the graphics card on PC Part Picker, it's a Sapphire SA-R9280X-3GD5-OC (11221-00-41G) 3GB DDR5 R9 280X OC PCI-E VGA Card, and it costs only $269. I am also unsure about this graphics card since when I added it to my system build, the wattage reading suddenly shot up, whereas it doesn't if I pick a nVidia card. Another question would be, should I get an ATX or just leave my mobo as a mATX?
http://au.pcpartpicker.com/p/vPhQMp
http://au.pcpartpicker.com/p/vPhQMp