I bought a tara lab ac reference that's suppose to be for a tv and it indeed made a difference on my Samsung plasma but not my Sony LCD.
I even tried it in my sons 22 inch LCD and no difference at all, then I went to my brothers house and connected it to his LG plasma and it made a difference in color and most importantly blacks.
I then went and bothered my cousin and replaced the PC on his projector and it made a difference as well..
So, has anyone changed their LCD PC and noticed a difference?