Two defective pieces in a row - unreasonable to demand refund?

A local merchant's policy might not be able to usurp local laws. between credit card protections and local governance, you might have options. 

Take the 3'rd lets face it, it's most likely not either the manufacturer or dealers fault its most likely the shipping company's that it failed on delivery. I'm sure Mac tries every piece they build so most likely its a shipping issue. there's thousands of reliable mac's out there from decades of use. so I'd not worry about the two issues they are not related anyway. also they are responsive and taking care of your issue with out delay I'd say that also has merit. 

The stereo Gods are telling you something.....listen,

1 was damaged. 1 doesn’t work. Get the third one. Really only 1 was doa. This happens. If the next one is doa, I’d demand a refund. 

You’re gonna have to order from someone. I would say third times a charm. I’ve been buying used Max for years and I’ve only had one problem with broken glass. I love their stuff and nothing holes or value as good as a Mcintosh. Give them a third chance see if they’ll upgrade you to even a better unit because that has such bad luck