If I'm wiring a bunch of speakers in parallel, is adding a resistor to the circuit path sufficient to protect the amp?
You can use a 70V audio line transformers. One connected in reverse to the amp and then each speaker has its own transformer, everything will remain matched and no power lost is a resistor. You need to size the one at the amp big enough to handle the power of all of the speakers then smaller ones can be used on each speaker.