Sorry to hear you are experiencing this situation. The facts stated, though, leave a lot of things unclear.
They would be liable only if there is reason to believe that the damage was either caused by or worsened by their negligence or carelessness. As opposed, for instance, to some undiscovered pre-existing defect in the amplifier, or some problem that may have developed during transportation. In those situations, as long as they noticed the smoke and turned off the amplifier quickly, Im not sure how they could be held responsible.
Also, whether or not they are insured has no relation to whether or not they are liable. Its effect would be, hopefully, on their willingness to accept responsibility, and perhaps on their ability to pay.
Has the root cause of the problem been diagnosed, and have they determined what was damaged as a result, and why? Has it been established if the leaky capacitor had anything to do with the smoking that occurred when they plugged it in, or for that matter with the noise you heard previously? Have they determined what part was smoking? When the smoke appeared, do they claim to have noticed it and turned off the amp promptly? Have they determined what the repair costs would be?
I dont mean to be discouraging, but Im not sure that anything meaningful can be said unless the answers to these kinds of questions are known.
Regards,
-- Al
