I guess a System like that would need loads of cooling and therefore alot of noise.
I bought and built a system not long ago and installed 3 fans. 2 on the case and 1 AMD heatsink fan. The stock AMD Fan was by far the noisiest fan I've ever heard. The case fans noise were easily solved by using a fan controller. I did away with the AMD fan and heatsink and installed water cooling. Now the whole PC is almost silent, just a slight humming.
I guess with the AMD 64 X2 will come with a Stock heatsink and fan so I would presume that its also going to be as noisy as mine.
Its going to be difficult in finding out how noisey a system is going to be without actually hearing the product yourself.
Remember, you can always silence PC's afterwards via aftermarket heatsinks and fans. Just like what i did.