MCH stands for the Memory Controller Hub (Northbridge)
ICH stands for the Input/Output Controller Hub (Southbridge)
The ICH voltages should never be changed, regardless of stability.
As for the vMCH, you should only increase this is if your system becomes unstable after 1450MHz FSB (~363MHz bus).
CPU Voltage should be changed before vMCH, to ascertain whether the CPU is to blame, or the motherboard.