ATI Raedon 5570 and three monitor setups

Hi,

I am having issues with displaying three monitors from my computer (i7 chipset and 16GB Ram). I have the monitors connected via dvi, hdmi and active display port adapter. Called AMD support and they told me that since my power supply is 300W max and the graphics card needs 400W minimum, i need to change the power supply to something atleast 400W to 500W to make all my three monitors to display.

I want to know:

a) Is it true? The power supply can be a reason for the issue? I hate to spend money if that is not the right solution

b) Can I get a 'Cooler Master eXtreme Power Plus 460W ATX' power supply even though it says the Combined +12V Rating = 312 Watts? Or should I get a power supply that has combined +12V rating more that 400W? Once again, i dont want to spend too much money on this unless i have to

I am very novice about this. Any suggestion is greatly appreciated!!

- Evan