The only problem with the NB47J heatsink on the A8N-SLI Deluxe is that it can interfere with 3rd-party videocard coolers. I got so tired of the whine of my BFG 6800GT fan, that I replaced it with the NVSilencer. But the NVSilencer is so bulky, it completely interferes with the NB47J. So I put the stock A8N-SLI fan back on the board.
Well, recently the whine of the A8N-SLI Deluxe fan got so annoying that I bought a Zalman VF700Cu for my 6800 GT. But even this cooler interferes with the NB47J, although much less so than the NVSilencer. I ended up cutting off a little bit of about 6 copper fins on the VF700Cu to get everything to fit without interference. I was very close to buying the A8N-SLI Premium to get around these problems altogether.