Okay, that's sort of what I thought. Do you think that duct helps much with cooling though? If I get an aftermarket cooler but it's not a tower cooler it might still work with that duct right? I guess there is only one way to find out...
It helps a little by providing a direct source of cool air directly to the CPU fan (rather than pulling warmer case air). Yes, it could work with a non-tower aftermarket cooler. Is it neccessary? Probably not.
That Zalman you linked is 62.5mm tall (2.5"). I'm guessing it would fit okay.
I have a 534 and actually the 'venturi' duct fits an 80mm fan, though a fan is not required since it is supposed to line up with the CPU fan. What you can do is place the fan between the case grille and the duct.
I had an 80mm fan installed on the duct in my case to improve airflow to the CPU HSF and found that it worked quite well. The duct is adjustable in height, but if you have a large HSF, you still may not have the clearance. Also, you must have a CPU fan that mounts facing the duct rather than perpendicular in order to make the duct functional.
ever thought about using that spot as another exhaust point? so you'd have a 120 intake in the lower front, a 120 intake in the lower side, a 120 exhaust in the rear, and an 80 exhaust in the upper side.