As has been confirmed earlier, - BIOS v1.20 for AMILO Xi 1526 / 1554 is also working with AMILO Xi 1546 / 1547.
The latest BIOS now, which is posted on Xi 1526 / 1554 support pages is v1.22.
So if you have Xi 1546 / 1547 you can go to the support pages of Xi 1526 / 1554 and download the latest BIOS there.
Note, that at time of this writing I have not flashed newest BIOS myself yet, on my Xi 1546, because it is left at home, but likewise with v1.20 BIOS, the v1.22 is most likely to work for us (the left out in the cold owners of Xi 1546 / 1547) as well.