I suspect that the reason for the blown speaker was DC passed through the Outs module. Simply because something has a balanced out doesn't mean that it'll block DC, and looking at Intellijel's docs on this, they mention nothing about isolation transformers...which IS how you block DC. But if you don't block it and push your amp and monitors really hard...well, this is what that looks like:
A better choice, which also kills ground loop issues, would be https://www.modulargrid.net/e/happy-nerding-isolator Stereo out, ganged level control, but behind the panel you've got transformers to balance the signal AND block DC. Plus, since you've got some "iron" in the signal path now, you can push the Isolator a bit harder and those transformers will add a touch of warm-up to the signal.