According to the DCC2 manual, which can be downloaded from www.emmlabs.com, the other analog line outputs to which you make reference are used solely when using the DCC2 as a DAC only and connecting the DCC2 to another preamp. The manual states in bold font that these analog outputs should not be connected directly to an amplifier.
If the gain offered by the DCC2 at maximum (i.e., 99) volume is, e.g., 8dB, would it make sense to either preset the volume on the DCC2 at a lower setting to achieve a lesser gain? Or, in the alternative, would it make sense to keep the DCC2 at the maximum setting and then, on the surround processor, program the output levels of the L & R to reduce the same by 8dB? If both are viable alternatives, is one considered the better alternative?