Hi,
I would go for the Zalman if I were going to make that change on this unit. Yes, do make sure it fits before you spill for that unit. However, I must give you another look at something you may want to consider.
I presently have an A8N-sli deluxe (not the premium) board with a San Diego 3700. I am using the factory heatsink and fan and running about 35c at-rest, and under 50c under-stress. It is a quiet unit. My case is one of the new Antec Sonata II models and I am using the standard 120 back fan and the auxillary 120 front fan. I have both of the fans in my case running at the slowest possible speed and no temp problems or noise problems. The power supply fan runs and the auxillary power supply fan (temp controlled) does not come on because the unit does not get hot enough. Total temps have a lot to do with case cooling, cables (round), and placement of fans.
Just thought I would pass that on FWIW, but my recommendation would be the zalman if you feel you have to put another one on this unit.