How to set up 2 monitors exactly with the same colours?

[bibo]

I have a Matrox P750 and I use it for video editing and CG in general.
I have 2 19" Compaq CRT monitors and I would like to set them up so they display exactly the same colours.
I have used DisplayMate (a powerful professional utility to analayse monitors) in combination with PowerDesk utility (fine adjusting RGB's Gamma), but I do not achieve the desired results - the Whites or Blacks of one monitor are always different from the other one. This is very apparent when I stretch any window over the 2 monitors: the background, either white or grey, is always visibly different between the 2. This is quite bothering!

Have you managed to perfectly adjust your 2 monitors?
How did you do it?
Do I have to use an external hardware Spectrophotometer?

Thanks.

Bibo

[Wombat]

Yeah, you'[ll probably need a photometer. Also, if the two monitors are just too far out of range, you might not be able to get their temperatures to line up.