The Intel fanboy's in hear are still in the closet. You obviously want to keep the socket, and even though I might have gone with a 165, the tight timings is a good point for going with the 185. But, for a cpu upgrade, and not a new system, the 185 is a good choice. Alot of people in here though think the only choice is Intel, and they are very quick to say it now that Intel can compete in the performance area. Don't listen, not a bad choice, not as fast as a new core 2 system, but, still blazing fast and you probably wouldn't NOTICE the performance difference between a what you have and a core2 based system in most cases.
wes
Edit: To keep from starting a flame war, we all know a Core 2 system would be faster, but, for the question you asked, the 185 or any dual opteron for that matter, is a good choice.