Looks like the Opteron 185 launched in March 2006. I don't have any experience with it but all the posts I saw seemed to think well of it. A number of posts commented that it was very similar to an FX-60 but with a locked multiplier and aimed at 24/7 server business. Seems to be around the -5000 level of performance; not sure what CPU you're running now.
It apparently sold for a bit over $1000 originally, hope the price has come down