My experience with the b206 is, that it is very silent. Like a gnome farting.
So you are using it with LinuxMCE ?
Assuming the B206 is the Nvidia ION version
Hmmm... no the B206 is the ATI variant of the Eee Box....I am actually writing this post on one ;-)
All the best
PS all of the current Eee range use the same basic fanned cooling system...and yes it is almost silent and very well engineered.