I'm with you on everything but this. I don't think you can damage the amp by trying to connect a pair of already-bridged outputs to a single speaker. If you happen to grab two of the same polarity you'll get no output. If you grap two of opposite polarity, you get a bridged output - the same as if you used one bridged output. You'd be using one pair of output transistors from each amp and the other pairs would be doing nothing. You don't gain diddly, but I don't see where it would hurt anything.

It's also possible to bridge an amp that doesn't have bridging built in. An amp capable of bridging is nothing more than an amp with one input reverse polarity (swap + and -) and then the output is reversed too (net result zero). If you put an inverting op-amp circuit ahead of one channel of a non-bridge-able amp and then use the + output from each channel the result will be a bridged output. .

Of course you might fry the amp if it can't handle the current. Minor details.

You can also do this with two identical mono amps, as long as the amps are not already bridged of course

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