In our opinion, true balanced/balanced is sonically inferior to dual-mono (separate left and right channels) in a single-ended configuration. AMRs background is in Single-Ended Triode amplifiers or SETs as these to our ears, is the pinnacle in audio design.
ALL AMRs including the DP-777 are dual- mono/single-ended. This costs more to manufacture but sounds the most gratifying. We actually wouldnt compromise on true balanced to satisfy the common notion of its being better.
For example, all Kondo Japan products are Single-Ended not balanced Mr Kondo (God bless) would rather not build an amplifier than make a balanced amplifier