If you have a 4000+ San Diego, the only differences between it and the FX-55 are 200 MHz and unlocked upward multipliers. It is simply a 2.6 GHz San Diego, and hardly worth shelling out $370 for, when the 4000+ is now selling for $135. Overclock the heck out of your 4000+, and if it dies, buy another one cheap. It should do at least 2.7 GHz at default voltage. I'm sure there are plenty of people here who can tell you exactly what settings to use on your motherboard for a painless increase to FX-55 speeds or higher.