I was researching further the D3x noise issue and I came across this test from popphoto. I do not know how the tests were performed, but here is a comparison between the noise levels of Nikon D3, Nikon D3x and Canon EOS 5D Mark II: the Canon seems to be better than the D3x at any noise level. Also, the D3 has better noise level (200 ISO) than the D3x?