I see nothing at all wrong with using the balanced inputs to your preamp, and using the single-ended outputs to your amp.
As far as great sonic benefits to using balanced, it would surely relate to your individual pieces of equipment. I don't have any balanced lines anywhere in my system, and I certainly am not feeling deprived of any "sonic goodness" because of that.
If your DAC and preamp have balanced topologies, then use the balanced outputs from your DAC. Since your amp has a single-ended topology, then use that output from your preamp. If the preamp or DAC are not using internally balanced topologies, and just have a transformer shoved into the line to provide a balanced connection, that is of no use whatever, in my opinion, unless you have some unusually long interconnect runs.
As far as great sonic benefits to using balanced, it would surely relate to your individual pieces of equipment. I don't have any balanced lines anywhere in my system, and I certainly am not feeling deprived of any "sonic goodness" because of that.
If your DAC and preamp have balanced topologies, then use the balanced outputs from your DAC. Since your amp has a single-ended topology, then use that output from your preamp. If the preamp or DAC are not using internally balanced topologies, and just have a transformer shoved into the line to provide a balanced connection, that is of no use whatever, in my opinion, unless you have some unusually long interconnect runs.