http://techgage.com/article/cpu-cooler-roundup---22-models-tackle-our-qx6850/7
They test really well, and are about the same, until you get into upper speed Ocs and the AC Pro efficiency tales off a bit. You shouldnt have install issues with either, because both have those heat-pipe bases which rise upo, and should clear those HSs on the ASUS. See the review, if you really wanna get into "superb" cooling, for such a nice mobo and CPU, consider: Thermalright IFX-14 Internal Fire eXtinguisher , if you check out this close up, you'll see it should clear them HSs. Though you probably wontbe able to use the extension. Its pricey though. Of course there's always the baddest of the bad boys: Thermalright Ultra-120 eXtreme but its OOS as usual, AND NE never carries them!!!!!!!!!!!!! (They never answer us why either when we ask.)
Of the 2 you've got in mind, I'd definitely look at the Zerotherm Nirvana: http://www.thinkcomputers.org/index.php?x=reviews&id=667&page=4
Peace, Penewah!
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