I don’t think the Amp can power 70V speakers and that sort of setup certainly isn’t supported.. I don’t know much about that tech, but I believe you would need an amplifier specifically designed to power 70V speakers.  It would make a lot more sense to get a 70V amp with a Sonos Port, if you’re looking for the ease of use Sonos provides or want to integrate other Sonos speakers.

A 70V amplifier would be a much better choice in this application. You can think of an AMP as approximately a 30V amplifier. If you dig around you can find discussions about 25V systems. Amplifiers designed for 8-Ohms are usually thrown into the 25V bin. 25V, 70V, 100V, or 8-Ohms are all the same physics, but different math. The voltage math is much easier to deal with when building large systems.

Would you like to tell me the price of these speaker?

Did a little more research on this out of curiosity.  So it looks like you could use the Sonos amp with 70V speakers, but you would have to put a ‘step up’ transformer in between the amp and speakers. The 70V speakers already have the ‘step down’ transformer built in, as well as the tap to limit power.  So yes, it could be done, and would allow you to connect more speakers with less wiring, and it doesn’t look like ohms would be a concern?

I still would go with a 70V amp Port rather than and Sonos Amp + step up transformer.  Seems like you are you using the products as they were designed that way.

https://www.proacousticsusa.com/media/wysiwyg/installation_help_page/helful_documents/Guide_to_constant_Voltage_systems_original.pdf

I’m not a fan of add on 70V matching transformers. They present an unexpected load for home audio amplifiers, often resulting in unexpected tripping of protection circuits, amplifier and transformer failure. A proper transformer is often out of the comfortable price range, encouraging potential buyers to skimp.