i have a simialr situation as you, although i am at 470 x 8....i can fold, game, encode...etc..dual super pi, all 3d marks...not orthos....instant fail or reboot...and i am running 1.575 cpu volts
excellent sound quality, i am very impressed, might not even install my audigy 2ZS on this mobo.
...on a different note....last night i started up the mobo for the first time, while loading windows it blue screened with 15 min left on the install, nvraid was the error...second install worked...