This is the first video card I have ever purchased for my primary PC that I did not feel compelled to immediately modify in order to silence. From the 9700 Pro I modified with a 1U heatsink, to an x850xt, to 2 x 8800gts 512mb in SLI (2 x Accelero S1), to the most recent MSI gtx260 Twin Frozr (for sale) (2 x 100mm speed controlled fans), I have never been satisfied with the stock cooling solution due to the noise character....at idle (the caveat)....until now.
Using software (Sapphire Trixx or MSI Afterburner), the fan speed can be lowered to a point where it should be inaudible in most any quiet case (I have an Antec P182; the front is 10 inches away facing me). From quietest to loudest, here is how it ranks versus the other 3 fans in the case:
(1) Scythe Slipstream (120mm, medium rpm version) - free standing in the front middle chamber and is rotating at around 600rpm. This fan is essentially silent.
(2) Sapphire 6850 at idle - fan speed at its lowest (although the software can indicate "0" the fan rotates at 1000rpm at its lowest). Very quiet. Unfortunately, as mentioned by another poster, it does have a slight clicking sound that can be heard from a foot or so away. However, it cannot be heard with the case closed (despite the fact I have 2 rear PCI brackets that are not covered).
(3) Scythe Flex (120mm, low rpm version) - it is connected to the cpu heatsink and rotates around 600rpm. Due to its connection, it makes a very low vibration hum that can be heard from a few inches away. The Sapphire and the Flex have the polar opposite noise characteristics but are about equally loud.
(4) Zalman ZM-850HP power supply. The 1000w model was reviewed favorably by SPCR as part of a silent build review. Its heat pipe heatsink, 140mm fan and larger than normal case contribute to its ability to output significant loads while remaining extremely quiet. I tried 2-3 other "quiet" PSU's before finding the Zalman. In all but the quietest builds, it operates unnoticed. That being said, the air flow noise from the PSU is now the noise floor of my PC. To remove the PSU from the noise floor, I would likely have to upgrade to a unit with a fan that does not spin at lower power draw (x650, x750, etc).
HDD noise is not an issue as I use SSD's. I have yet to find a truly quiet 3.5" HDD....have tried them all and none of them are near quiet even when hanging via elastic string at the bottom of the P182 that sits in a cabinet with a closed front (but open back. IMO, you can't have a truly quiet PC (let alone silent) using mechanical drives.
Caveat
Above idle, the Sapphire is not quiet. If you have a quiet PC, the Sapphire 6850 will become the noise floor once you begin gaming. Hopefully the audio will drown it out. If it does not, the Sapphire will join the rest of the video cards I've owned and will be modified with larger fans.
Speaking of which, has anyone taken off the cover off of the Sapphire to determine exactly how large the heatsink is? I'm hoping it's wide enough to support 2 x 100m fans (or smaller if necessary). This would allow for an easy but efficient dual fan mod - 1 fan always operates at low rpm while the other fan runs only when triggered by a certain temp. For, e.g., the above-mentioned gtx260:
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