i can´t answer your question, but i decided to make bride of zen, because i don´t own any balanced source or amp, and i think simplicity has it´s own aesthetically quality. I´ll build it with a array of relais instead of the pot for volume control, so this part will be more complex than the main circuit.

If You decide to make a blanced, why not this?

or as Gabster (thanks to Gabster) gave the link :