Why do you guys think the intercooler moves more air when running off of its own PSU? The pass-through connection allows it to draw power from the 360 PSU's 12v rail, so replacing that with its own 12v adaptor WILL NOT increase fan speed, and, therefore, WON'T INCREASE AIR MOVEMENT because it's the same voltage. Unless your trying to make the case that the 360's PSU doesn't have enough amps to run both the 360 and the Intercooler, which is also completely ridiculous.
Here is a link to an article which clearly states that the maximum power consumption for the 360 (in games) is a maximum of 186.5 watts, while the 360's PSU supports 203 watts. That's 16.5 watts of spare power, while the intercooler's fans only use a total of 4.68 watts, but if you don't believe the math, look at a modded 360 like Dano2k0's internal liquid cooling job. He's running a liquid cooling pump, fans for the radiator, and leds all off of the stock PSU. The only thing a seperate PSU is good for is letting the fans stay on after the 360 is off. Sorry if I seem a little blunt, but I've heard this claim that a seperate PSU will increase airflow many times and have seen absolutely no proof to back it up.
I understand what you are saying but for whatever reason switching my Intec cooler off its own 12v 500ma psu to one I found in my basement thats 12v 1a it hauls ass moving a ton more air. I believe the key here is "ma" . The cooler will only draw what it needs which is 12v but not sure about ma. It just works better and I am now very pleased with the performance of this cooler. It sucked a napkin to the side of my 360 like a vac cleaner and held it there till i turned the cooler off. It never did that before. In the words of Tim Allen "NOW THATS MORE POWER" grunt lol