The only thing I know is that, under certain circumstances, multiple ADC and DAC conversions do not substantially degrade the sound. I heard a track on a test CD (a Jazz sampler/test signal CD by Chesky Records) that was of a sample of music that had been converted back and forth a hundred times, and the same track that had been converted only once. I don't think I could reliably tell the difference.
I don't expect the additional conversion of the OKTO to hurt the sound much, but, then again I don't see how it would help to take a digital signal and convert it to analogue then have an ADC convert it back to digital for processing in the DBX.