Hello Marcink10, if I were you, I would get the Rotel RA-1570 integrated amp instead and sell your RA12 to drive your B&W CM6 speakers. The CM6 are great speakers, you would want to have a better integrated amp to pair with. The RA-1570 is quite a bit better than your RA12.
The RA-1570 has decent built-in DAC but if you want to get the Rotel RDD-1580 standalone DAC it will even be better. The RDD-1580 standalone DAC unit has exact same Wolfson DAC as the one that is used in the RA-1570 integrated amp, however, the RDD-1580 has two DAC chips, one for each channel and the RA-1570 integrated amp has only one DAC chip. The RDD-1580 has lower noise & distortions thus will improve the overall sonic performance of your system. The RDD-1580 is a great sounding DAC unit and had very good reviews on The Absolute Sound and few other audio magazines or sites. But you can also use the DAC in the RA-1570 integrated amp. It is a good decent DAC. Hope this helps. Let us know what you decide on.