Didn't your X2 come with the AMD heatpipe cooler?? Which is more than adequate for 2-6-2.8 Ghz (which is all you will get out of that chip).
The aftermarket coolers are only slightly better than it, maybe a bit quieter.
I don't think the 3800s come with the stock heatpipe cooler. My AM2 didn't. My rig was getting too hot for my comfort (55+C) with a 400Mhz oc. I got the Zalman 9500 and couldn't be happier with it! My load temps with the oc are <45C now.