As far as I experimented using the TPA6132 breakout and the isolation transformers is the only solution that solved the problem (as it actually breaks the ground loop, while a 5R resistor would attenuate the loop).
I think it is also the safest way to go as the daisy seed output is protected with the tpa breakout.
These breakouts and transformers are quite low cost and easy to find (i bought them from amazon).
[edit] if you go for separating AGnd and DGnd with a small resistor and worry about eventual damages caused by potential differences between them, you can add a pair of schottky diodes as described here. Their low threshold voltage will protect you from such hazards.
