DAC gain, or amp volume?

Generally speaking,is there any advantage in using a higher gain setting on a Benchmark DAC1, and less volume on the amp? Or is it better the other way around?
Found out last week my Mini-DAC's gain was set *way* high. Sonic effect: harshness in upper mids, congestion, little play in the preamp's volume control. Got this advice: if you are using a tube preamp you may be able to work with a higher gain setting than the conventional input level of around 2 volts. A solid-state preamp could overload if your DAC's output level is too high.
Volume should be set so that you get max power at 1 o'clock position. On XLR outputs 0dB has lowest output impedance (if it makes difference) followed by -20dB (-10dB is the worst at least on mine). New version of Benchmark has stronger amps and different dividers. Earliest Benchmarks had very high output impedance on RCA outputs and should be moded.