yea it should be fine with the standard NB fan, not sure about any custom ones tho! I know for a fact that this one will tho, and its a good one, average load temps of around 30:
http://www.overclockers.co.uk/showproduct.php?prodid=HS-027-ZA&groupid=701&catid=57&subcat=821&name=Zalman%20CNPS9700-NT%20nVidia%20Tritium%20CPU%20Cooler%20(Socket%20754/939/940/AM2/LGA775)
I have no better suggestions, don't know much about SLI, but for what you want this seems lie a good MoBo. All i can say is that NForce chipsets dont overclock well. Is that what you want the heatsink for?