I remember I was told that my Dynaudio Focus 140 were "hungry speakers" that required a very powerful amplifier in order to get them to perform well. Several reviews and assessments say your amp should be able to deliver 200W to do them justice.
I have them connected to my Beolab 5000, and I have never had the volume above 6, it's simply too loud. The Beomaster 6500 will have no difficulty "driving" the 150s, unless you intend to install them in a discoteque to have 600 people dancing to them. 