MOTM

> Would the 3 op amp solution be an inverting buffer for signal +, a
> non-inverting buffer for signal -, and then the third to sum the outputs
of
> the first two?

Charles Stella just posted a hint on 2 other SSM chips.
Take a look at the block diagrams (data sheets at www.analog.com)
Replacing a transformer at the output is even more involved
than on the input, if you really want it "floating" (but still within
the supply voltage bounds).

JH.