Hmm, well that means you don't need a modded ROM, this default ROM is already 99 Watts, so should be able to have even 6 of these cards on a 1000 Watt PSU.
The only benefit I see for making a custom ROM is trying to get the VRAM higher default clocks and Lower the CORE Voltages and clocks to be more effecient.
That's weird. I most certainly cannot fit 6 of these on a 1000w. My kill-a-watt puts it over 1000. I guess try to crank down the core and I'll test it.