I have the ZM80A-HP with a 92mm Acoustifan (I used the 92mm Zalman one
for a while but changed over to the Acoustifan recently when I
replaced some case fans) on my GeForce4ti4600 card.

I find the heatsink brilliant and very effective. I don't overclock
anything and have never measured temperatures on it, but even after a
heavy gaming session the card is never more than "warm" to the touch.
You will notice how well the heatpipe works - the back side will get
warm too very quickly. Oh, it IS a big heatsink, check you have space
for it please.