Sony PSU replacement

I have a Sony PCV RZ 40C1b desktop computer and I am looking to upgrade my graphics card.

The power supply that comes with my Sony is rated at 295w maximum, however all the graphics cards I am interested in purchasing all draw 350w

Does anybody have any experience with replacing the PSU in this model of Sony and if so any recommendations as to a 3rd party PSU suitable for this computer?

I have installed a ATI 1550 8x AGP at the moment because it only draws 280w but it is woefully inadequate for my purposes.

I've been told by Sony that there is a chance my motherboard may fry if I install a more powerfull PSU but that could just be the company line.

Short of tossing the unit into the bin is there anything I can do?

Any help would be greatly appreciated.

Thanks