http://forum-en.msi.com/faq/article/power-requirements-for-graphics-cards
Do cntrl+F and put in 270 and press enter. The site says 500 W MINIMUM. I am paranoid and would get a 600W Bronze. I deal with servers and PC's in my civilian job all the time that are built with the MINIMUM PSU requirements and they are the ones that fail by far the most.