Honestly, there's really not much point in going much upgrading this system
due to the proprietary nature of the motherboard . There is a version
5.51.28.50 BIOS with a Dec 2007 release date for the A8M2N-LA motherboard.
Whether or not this update provides support for the more newer X2, FX and
Opteron dual core lines I don't know. Release notes were hard to find and I
can't be bothered to dig a whole lot deeper. It's your box, after all.  If
it could, then get an Opteron 185 which is a 2.6Ghz 2Mb L2 cache unit. It
(other than the FX60 which is basically identical other than being fully
unlocked rather than partially like the Opteron and four time the cost) is
the ultimate and final sokcet 939 upgrade. You'll really see a difference
with it.....if the BIOS can be upgraded to support it. Don't just buy one
off eBay and stick it in, without checking. About $210.