I found a nice amplifier from German based comapny Restek.

The name of the amplifier is: Restek Vario (www.restek.de --> archive --> Vollverstärker)

I thought production ceased out long ago, but I called them and it can still be ordered (last December).

I use the B&O aktive modul with my old ACRON 600B (which sound much better tha Beolab 1) but if you have better (passive) speakers
 than you migth think about it...