Havent heard a reference cooler yet. But ive got a BFG 5900NU which uses the same cooling as the BFG 6800gt OC if memory serves correctly...and to me I cant hear a damn thing
I really can't speak about the card you are refering to here, as I own a 9800 Pro. What I do want to suggest is that if your video card has a noisey HSF, replace it with a VGA Silencer. They make them for both nVidia and ATI chipsets now. I put one on my 9800 and the noise level out of my rig dropped noticably. My card temps also went way down as well.
Dunno 'bout the stock one, I've heard it's audible if your system is relatively quiet... My BFG came with a two-fan model that didn't have a good rep so I just replaced it with an NV Silencer 5 (the model that replaced the VGA cooler from Artic Cooling mentioned above), pretty satisfactory noise-wise; nice temps for sure.