I have installed now a Noctua NF A4x10 distributed by Amazon. It is a litte bit noisier than the Blacksilent fan but much more quiet than the original AVC  

. Though the cooling power does not quite reach that of the AVC it seems to be plenty enough. The fan starts and  rotates in low mode - never went up to high mode yet. Also I went back to FW 1.01 where the fan switches off when the disks are not in use, which  was not the case with 1.02 or 1.03  

. The latter ones show temperature in the configuration menu, 1.01 does not  

. Temperature is ok, however, as one can check with disk temperature in the menu. 
I have to add that tempereture is shown when I use firefox instead of Chrome 

Have fun
alzi