Should do at least 2.5GHz (2.7 - 2.8GHz average). This is the retail version with 3 yr warranty. Socket 939 with 90 micron die, 67W power envelope, 2GHz core speed (10x multi). E4 stepping with 1.4 Vcore. FREE SHIPPING, but tax in Ca and Fl.
http://www.amdcompare.com/us-en/opteron/Default.aspx
Cheapest OEM A64 3000 with 1.8GHz core speed is around $53.
http://www.wiredzone.com/itemdesc.asp?ic=30685800