Hi,
this is not a special problem of the Beosound 5! It affects ALL digital audio systems that use data of ripped CDs because it depends on the recording on the CD itself.
There are software tools to adjust the soundlevel of your entire music collection; but this must be used very carefully because it can damage audiofiles that are already loud enough.
I hope B&O will release some kind of adjusting function like iTunes. This will not affect your audiotracks.