You have a really nice preamp that adds no noise or distortion to the music path. I would go with using the Benchmark pre for volume control. You should then turn the dac volume to 100% so you get the full signal going to the pre. The way it was explained to me is you want to push a full signal to the last car in the train before attenuation.
When I inserted the Benchmark pre into my system, I noticed immediately better sound at lower volumes and much much better and granular volume control than the dac. You may have to adjust the pads at the XLR outlets to properly match your components but that is better explained in the user manual of the Benchmark.
When I inserted the Benchmark pre into my system, I noticed immediately better sound at lower volumes and much much better and granular volume control than the dac. You may have to adjust the pads at the XLR outlets to properly match your components but that is better explained in the user manual of the Benchmark.