w/Opteron 185, I picked up a new Zalman CNPS9500A Ultra Quiet CPO Cooler. It is recorded within the text body of the thread I mentioned. My hot CPU stayed cool even after 15 minutes of full load after that pure copper Zalman cooler was installed.
Well, I am now using an AM2 Athlon 64 X2 6400+, so 3200 MHz. The Opteron 185 I had ran at only 2600 MHz. The TDP between the two are similar, 110 W vs. 125 W. The AM2 does feel a bit faster, most noticeably on booting. I'm not sure if it is just due to the freq. difference, or the technology.
Because of the mounting of the AM2's CPU card, I am now using an FX-8100 cooler. https://www.ebay.com/itm/302870552783 It has this annoying feature that ramps up/down CPU speed based on CPU temperature, irrespective of using the 4th CPU power pin or not. It can get damn loud, so I had to use a voltage trimmer to allow for a max voltage of around 7 V. In which case, the max speed has a tolerable noise. It works well enough, but I'd like a non-AMD CPU cooler, but due to the profile of the CPU-card, finding one may be stressful.
Plan your life wisely, you'll be dead before you know it.