Caporegime
I run an MSI R9 290 Gaming OC off a 500W Corsair CX500M with no issues.
Also running of it: an MITX board, 3570 at stock, 2 sticks of RAM, SSD, Corsair H75 AIO water cooler and 2 92mm case fans as well as the usual external keyboard, mouse, xbox controller, usb headset and USB hard drive.
ok These things run @ 300 Watts stock, it just looks a bit tight.