Well they usually do some VMods, not only to get higher but also more stable voltages, you know some capacitors, once i saw an article on some guys that added another power phase to a P5B, and replaced most of the power components on board.
Maybe they use non top models because the better power stage wouldn't be enough for their needs, and they would need to mod the board anyway.
That, and a very complex
BIOS would probably just get in the way as you don't exactly have a week to tweak various parameters while your buddy pours LN2 in the pot and 2 volts are running through the
CPU.
