Sorry, this computer doesn't allow me to type Chinese at the moment.

I think two PSUs can still be applied when the power paths are all independent.

Take Raziel's case for example, we can use two PSUs A and B, both are 500W

Then you can use PSU A to supply motherboard, CPU, HDD and optical devices.

For those 4 pieces 9800GX2, we can arrange the PSU B purely to be the power source for these crazy stuff, and we should NOT connect PSU B to any other more devices, especially connect your motherboard with PSU A together, this is very unwise !

Thus, we can make sure the PSU A and B will not interference each other without any redundant design, aka, O-Ring ciruit.

In other words, it is better to avoid two PSUs from "seeing" each other through the power path of your computer.