|If it didn't work outside the case, why would you bother installing it?|
Are you sure you benchtested correctly? To do it you need the board, CPU w/HSF, one stick of RAM, keyboard, power supply & monitor...nothing else. The monitor should be connected to the onboard video & both the 24-pin main ATX plug & 4-pin ATX12V need to be connected to the board. Turn on the monitor & power supply, then power up the board by momentarily shorting the two power switch pins with the tip of a screwdriver.
How to Bench Test Your System