The reason for the above is this: Most heatsinks for AMD use a retention bracket, most for S775 use the push-pins. Either way, when your motherboard is on the stand-offs and your applying pressure, the PCB bends and stays that way. Eventually, it bends to where the CPU cooler is not making as much contact or pressure as it should, same goes for the mosfet coolers. So, always install the CPU, paste, HS+HSF, and RAM before the board goes into the case.
I can say everything I just did from experience. My motherboard is bent like hell
.