The ECS GTX460 Black is the quietest video card they have tested at Guru3d, including all the recent releases. The key is it's Arctic Cooling Twin Turbo Pro cooler. The ECS Black comes in at 37dB at full load, vs. the Hawk and Cyclone at 43dB. The 6850 is close at 38dB:
http://www.guru3d.com/article/ecs-geforce-gtx-460-black-review/8
http://www.guru3d.com/article/radeon-hd-6850-6870-review/11
It is also one of the fastest, with plenty of headroom to overclock. Performance is on par with the 6850, except when you overclock, the ECS Black shows greater potential. At max overclock, on an identical setup, these reviews show the Black beating the 6850 by between 27-10 fps, except at 2560x1600 resolution:
http://www.guru3d.com/article/radeon-hd-6850-6870-review/21
http://www.guru3d.com/article/ecs-geforce-gtx-460-black-review/18
As an added bonus, it's only $179 at Newegg after rebate:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814134117