Well, I've had the same problem on my A8V-MX. While the safety zone for a 90 nm K8 extends up to 1.55V, the lower the voltage, the cooler and healthier the CPU.
For lowering the Vcore, you can go in the bios and drop the reference voltage there if the bios allows this. If it does not, you can do as I have done; Install RMClock (download from www.rightmark.com) and you can set different voltages for every power state of the CPU.
My board, supplied the 3000+ with about 1.50V but with RMClock, I set it to run with just 1.25 on load (Venice cores undervolt pretty well) and load temps dropped by 8-12°C. The same way I undervolted the X2 4200+ from 1.40 to 1.35; temps. went 5°C down.