I have the asus A7M266-D board with MP2800's. I am running the vcore at 1.6v.

I have heard that you can run these much lower to help lower cpu temps. Is this true and how low can i go? If I go too low will it hurt my cpu's?

Won't hurt the CPUs at all. Actually, if will allow them to run cooler, which will only benefit your CPUs. As far as how low, that's really for you to test and figure out. When you get to a voltage where the system won't boot, or where Windows isn't stable, you've gone too far

I have a A7M266-D board, and I just got 2 2800s... would anyone recommend changing to the Gigabyte board?