I bought a Dynatron A46G for my AMD X4 620 AM3 Quad Core CPU.  Just judging by touch, the stock OEM fan/heatsink combo kept things so cool, I could leave the 1U server on the floor and it barely felt warm to the touch, including the heatsink itself.

I thought the Dynatron A46G would be enough with passive cooling (it has no fan), but the same setup became burning hot on the underside of the server and also by touching the heatsink itself within minutes.

I thought that the Dynatron A46G wasn't doing a good job and thought the stock heatsink without a fan (disconnected) would be better.  I was wrong and got the same results with the stock heatsink, it's amazing how a tiny fan adds so much extra cooling.

Now I need to find another solution or find a way to get more airflow via a small 40MM exhaust fan and see if that helps with the A46G.