An alternative is to use a server cooler, such as the Dynatron A46G, and to attach a low-speed 80mm fan (I used high-strength double-sided tape on the four fan corners).
I have an X2 4200+ being cooled with this heatsink with an 80mm fan in a low-profile SFF case, and even at <1200RPM the CPU stays under 45C at full load. The heatsink itself is just over 0.9" tall. If you go this route, you may want to test with the fan pushing vs. pulling air, as I found pulling to be more effective in my setup.