http://www.madshrimps.be/?action=getarticle&articID=473
Cheep: 40mm fan and thermal grease. I'm not 100% sure how people are mounting those, but it should cover any overclocking you can pull off with that motherboard. And should cool better then almost any 3ed party northbridge cooler.
Affordable: passive Zalman ZM-NBF47 I managed to mount it on my AN8-SLI and its works so-so, just mounting it was a
major pain in the ass. But unlike the review I managed to install it in a way so that I could still use the top pcie slot/ *Note this cooler will require some air flow to work, in my case it's getting its extra air flow from my Zalman video card cooler also it could interfere with long video cards.
Costly: that Jin Ting or a Swifttech active northbridge cooler.
And yes those Asus stock chipset coolers suck at everything except bugging the hell out of you.
I went with the zalman because I was working on making my computer quieter.