I just got this response from AeroCool:
Power Supply design is a very special and complicated technology, PSU converts different voltage of input power into different regulated voltage output power. Different type/function of switching power supply has different requirement, even Intel's official released "ATX12V Power Supply Design Guide" just provides design suggestions and reference specifications for power supplies that comply only with ATX Specification motherboards and chassis.
According to Intel ATX12V power supply specification, there are different voltage of output power (+12V1DC, +12V2DC, +5VDC, +3.3VDC, -12VDC, +5VSB), each voltage has its Min., Max and Peak current output specified in manufacturer's PSU specification. There is also a Cross Loading Graph for typical power distribution for any rated wattage PSU which is the combined power for 12V, 5V and 3.3V for each PSU.
The combined power is defined as when different voltage of output current are combined together, the maximum power can achieve at the same time. For example, in our Zerodba 620W PSU, the max output current for +12V1 is 20A (12x20=240W), +12V2 is 18A (12x18=216W) but our combined output wattage for 12VDC is 360W (not 240+216=456W). The combined power for +3.3V and +5V is 280 W, but our combined wattage for +3.3V,+5V, +12V1 and +12V2 are 600W (not 360+280=640W), these figures are tested and specified by PSU manufacturer, some manufacturer may be too conservative or too aggressive. (some may use peak load)
In addition, there is a power limit set by UL1950/CSA950/EN60950/IEC 950 that "Under normal or overload conditions, no output shall continuously provide more than 240 VA under any conditions of load including output short circuit", this is why the maximum out current can not exceed 20A for each +12V output voltage power line. If you check with all the PSU on the market, you will know the max. output current are less than 40A (most of them are 38A). Our Zerodba 620W have max output of 38A which will meet SLI requirement.
So, from the above explanation this PSU should support the ATI cross-fire.
As you can see in the last paragraph AeroCool clearly states that their Zerodba power supply has 38A on the 12V rail.