The motherboard is a Printed Circuit Board that connects other components that use power. Asus recommends using a minimum of a 300 watt power supply. Add-on video cards might require much more power than the minimum 300 watt power supply Asus recommends.
I don't know exactly what motherboard you are referring to but I can tell you that of the three listed below, the M5A78L-M LX doesn't support the FX-8350 CPU.
1) M5A78L-M LX
2) M5A78L-M/USB3
3) M5A78L-M LX V2