I would simply use a buffer on one, or both, of the outputs if impedance is an issue. There's always more than one way to skin a cat.
Kal, I believe that would obviate your concens about overloading, or causing an impedance mismatch, with the output stage of the preamp.
Kal, I believe that would obviate your concens about overloading, or causing an impedance mismatch, with the output stage of the preamp.

