Sorry, but this question has been bugging me for a while, and probably should be in the Zkit1 forum.

I know these can be mono amps by connecting the outputs in series and feeding the same signal into both inputs, but will this work?

1)  Use differential (balanced) output from DAC.
2)  Feed non-inverted wire to left input.
3)  Feed inverted wire to right input.
4)  Connect ground wire to both negative inputs.
5)  Connect both negative (floating) outputs together.
6)  Connect speaker to the remaining two positive outputs.

Not only will I get twice the voltage across the speaker, but any noise picked up along the way should be equal on both sides of the speaker and get cancelled out.  

Mike